The consent submitted will only be used for data processing originating from this website. Type in any integral to get the solution, free steps and graph. is the Dirichlet eta function. is a cube root of unity. 126-131). (Glasser and Zucker 1980). A positive even number can be represented by , where is a positive integer, giving the infinite sequence . The preeminent environment for any technical workflows. Wolfram Web Resource. Sequences, Sums & Series In the Wolfram Language, integer sequences are represented by lists. tensors, respectively. Central infrastructure for Wolfram's cloud products & services. and The Summation Calculator finds the sum of a given function. Is there another way to represent this summation? Repeated indices are implicitly summed over. denotes any function (Glasser 1974). How to use the summation calculator Input the expression of the sum Input the upper and lower limits Provide the details of the variable used in the expression All Functions Operators Functions Interact on desktop, mobile and cloud with the free WolframPlayer or other Wolfram Language products. Knowledge-based, broadly deployed natural language. Some of our partners may process your data as a part of their legitimate business interest without asking for consent. for contravariant and covariant Knowledge-based, broadly deployed natural language. Define a recursive sequence using RecurrenceTable: Compute the Sum of a sequence from its generating function: Use ESCsumtESC for a fillable typeset form: Calculate a generating function for a sequence: Generate power series approximations to virtually any combination of built-in functions: O[x]9 represents higher-order terms that have been omitted; use Normal to truncate this term: Given an unknown or undefined function, Series returns a power series in terms of derivatives: Convergent series may be automatically simplified: Revolutionary knowledge-based programming language. Finding valid license for project utilizing AGPL 3.0 libraries, How to intersect two lines that are not touching. You might also like to read the more advanced topic Partial Sums. $${\large \sum_{ \small x=1}^{\small n=10} x^{(-1/3)}}$$, $${\large \sum_{ \small x=1}^{\small n=10} x^2+2*(cos(x)+\sqrt{x})}$$, $${\large \sum_{ \small x=1}^{\small n=10} 2x*(x-1)! Then the sum is infinite and the symbol is used as if it were a number, like this: Even if the terms get smaller, the partial sums may still grow without bound as more terms are added. Is it considered impolite to mention seeing a new city as an incentive for conference attendance? Can we create two different filesystems on a single partition? 5), who later jested to a friend, "I have made a great discovery in mathematics; I have suppressed the summation sign every time that the summation must be made over an index which occurs twice" (Kollros 1956; Pais 1982, p.216). are invalid because the index appears three times in the first term of (), while the non-repeated Instant deployment across cloud, desktop, mobile, and more. Enter what you want to calculate or know about. automatically selected method. Step 3: Substitute the series values in the above equation. , xk, we can record the sum of these numbers in the following way: A simpler method of representing this is to use the term xn to denote the general term of the sequence, as follows: In this case, the symbol is the Greek capital letter, Sigma, that corresponds to the letter 'S', and denotes to the first letter in the word 'Sum.' In practice, the convention tends to occur alongside both the Kronecker delta and permutation symbol. 51K views 3 years ago PRECALCULUS | Mathematical Induction This is an introduction to the Summation Notation with examples on how to write and evaluate sums by expanding the terms. as. Wolfram Research (1988), Sum, Wolfram Language function, https://reference.wolfram.com/language/ref/Sum.html (updated 2019). The first item on the above list can be employed to greatly simplify and shorten equations involving tensors. "Sum." Connect and share knowledge within a single location that is structured and easy to search. In [1]:= Out [1]= https://mathworld.wolfram.com/DoubleSeries.html. More compactly, sequence notation is used: means . It follows immediately that if is perpendicular to . Choose "Find the Sum of the Series" from the topic selector and click to see the result in our Calculus Calculator ! MathWorld--A Wolfram Web Resource. Technology-enabling science of the computational universe. "HypergeometricTermFinite". By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Find the sum of the first 10 prime numbers. If the sequence is finite, the last term is shown, like . indices, A finite double series can be written as a product of series, An infinite double series can be written in terms of a single series, Many examples exists of simple double series that cannot be computed analytically, If the number of terms is infinite, the sequence ends with "", like this: . Repeated indices are implicitly summed over. An infinite series may or may not have a finite sum. For infinitely many terms, the notation is , which stands for . A sequence is an ordered set of numbers that may have a finite or infinite number of terms. Revolutionary knowledge-based programming language. Thus, for n = 10, Euler's phi function ( n) (which counts the number of positive integers less than and relatively prime to n) can be expressed as. Curated computable knowledge powering Wolfram|Alpha. "Sequence and Summation Notation" Download Wolfram Notebook Let a closed interval be partitioned by points , where the lengths of the resulting intervals between the points are denoted , , ., . Summation calculator is an online tool that calculates the sum of a given series. Transcribed image text: 2. ]}, Enable JavaScript to interact with content and submit forms on Wolfram websites. If you would like to change your settings or withdraw consent at any time, the link to do so is in our privacy policy accessible from our home page.. Wolfram Research. Browse other questions tagged, Start here for a quick overview of the site, Detailed answers to any questions you might have, Discuss the workings and policies of this site. Compute answers using Wolfram's breakthrough technology & knowledgebase, relied on by millions of students . Decimal to Fraction Fraction to Decimal Radians to Degrees Degrees to Radians Hexadecimal . summation. Of course, it's hard to say for sure, since you don't mention your specific application. Spellcaster Dragons Casting with legendary actions? Identities involving double sums include the following: over binary quadratic forms, where the prime indicates that summation occurs over all pairs of and but excludes the term . The notation for a series with finitely many terms is , which stands for . Step 1: First of all, lets identify the values. $${\sum _{i=0}^n\left[f\left(x\right)\right]}$$. You might be able use boole, which returns $0$ or $1$ depending on whether it's argument is True or False. (1) where is summed over for all possible values of and and the notation above uses the Einstein summation convention. (1) where is the angle between the vectors and is the norm. Use Product to check , a function found by the mathematician Euler. Formulas for two basic finite series are. Notation create a custom notation for input and output, Symbolize force a box structure to be treated as a single symbol, InfixNotation force a box structure to be treated as an infix operator, RemoveNotation remove a custom notation, RemoveSymbolize remove the symbolization of a box structure, RemoveInfixNotation remove the definition of a custom infix operator, ClearNotations clear all custom notations, symbolizations, and infix operators, AddInputAlias add an alias in the current notebook, ActiveInputAliases list of active aliases in a notebook, UpdateNotebookStyles add the custom style and input alias notations to a notebook, Enable JavaScript to interact with content and submit forms on Wolfram websites. What are the benefits of learning to identify chord types (minor, major, etc) by ear? Revolutionary knowledge-based programming language. You might be able use boole, which returns 0 or 1 depending on whether it's argument is True or False. try each method in parallel until one succeeds. The Wolfram Language can evaluate a huge number of different types of sums and products with ease. sigma notation. Step 2: Click the blue arrow to submit. Get this widget Build your own widget Browse widget gallery Learn more Report a problem Powered by Wolfram|AlphaTerms of use Share a link to this widget: More Embed this widget }{\sqrt (k+10)!}$. United States Salary Tax Calculator 2023/24, United States (US) Tax Brackets Calculator, Statistics Calculator and Graph Generator, Grouped Frequency Distribution Calculator, UK Employer National Insurance Calculator, DSCR (Debt Service Coverage Ratio) Calculator, Arithmetic & Geometric Sequences Calculator, Volume of a Rectanglular Prism Calculator, Geometric Average Return (GAR) Calculator, Scientific Notation Calculator & Converter, Probability and Odds Conversion Calculator, Estimated Time of Arrival (ETA) Calculator, Provide the details of the variable used in the expression. The preeminent environment for any technical workflows. It can find the simple sum of numbers as well as the Sigma notation sum of any function. A complete table of the principal solutions of all solvable is given in Glasser and Zucker Use Sum to set up the classic sum , with the function to sum over as the first argument. In calculus, infinite sums and products can pose a challenge to manipulate by hand. Explore with Wolfram|Alpha More things to try: 10th partial sum of 1/n^4 fourth partial sum n^-2 100th partial sum of 1/ ( (n+1) (ln (n+1)^3)) Cite this as: Weisstein, Eric W. "Partial Sum." From MathWorld --A Wolfram Web Resource. use iterated univariate summation. We and our partners use cookies to Store and/or access information on a device. Then the sum is infinite and the symbol is used as if it were a number, like this: Stack Exchange network consists of 181 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers. . The sigma notation is used to evaluate the sum of the function by placing the lower and upper limit values. Evaluate n = 1 12 2 n + 5 Sigma (Sum) Calculator Just type, and your answer comes up live. Pi 2. Free Pre-Algebra, Algebra, Trigonometry, Calculus, Geometry, Statistics and Chemistry calculators step-by-step. How to determine chain length on a Brompton? From MathWorld--A What is summation? Besides numbers, other types of values such as functions, matrices, and vectors can be summed as well. The x^2 is also absorbed into the power series: In [10]:=. Find the Sum of the Infinite Geometric Series Find the Sum of the Series. We and our partners use data for Personalised ads and content, ad and content measurement, audience insights and product development. Get the free "Summation Calculator" widget for your website, blog, Wordpress, Blogger, or iGoogle. https://mathworld.wolfram.com/EinsteinSummation.html. Updated in 1996 (3.0) To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Sum. Central infrastructure for Wolfram's cloud products & services. It can also be referred to as the algebraic sum of numbers or quantities. Natural Language; Math Input; Extended Keyboard Examples Upload Random. Showing $\sum_{\alpha=0}^k \binom{k+15}{\alpha + 10}\binom{k}{\alpha}=\frac{2^{2k+15}(k+6)(k+7)\left(\frac{2k+15}{2}\right)! Using the 1988. Powered by WOLFRAM TECHNOLOGIES
To view the purposes they believe they have legitimate interest for, or to object to this data processing use the vendor list link below. https://mathworld.wolfram.com/DoubleSeries.html, sum (sum (-1)^n 2^k from k = 1 to m) n = 0 to 2, sum (sum i/j from i = 1 to j) from j = 1 to n. Experimentation in Mathematics: Computational Paths to Discovery. special finite hypergeometric term summation. Wolfram Language. The partial sums may grow without bound, like for the series . Generate the results by clicking on the "Calculate" button. image/svg+xml. Solve geometry problems, proofs, and draw geometric shapes. A double series that can be done analytically is given by. Step 2: Place the given function in the summation equation. Wolfram Language. Improving the copy in the close modal and post notices - 2023 edition, New blog post from our CEO Prashanth: Community is the future of AI, Wolfram|Alpha Plotting multiple geometric objects. A simple Summation (AKA Sigma Notation) calculator. where }$$, $${\large \sum_{ \small x=1}^{\small n=10} cos(pi*x/10)}$$. Hence the sum of the first 10 prime numbers is 129. Now look at this infinite series (the harmonic series): (a) Write this series in summation notation (b) Now, calculate the following partial sums numerically (You can use your calculator or Wolfram Alpha) (c) Remember that we determine convergence of an nfite series by taking the l of the partial sums. Last Modified 2019. https://reference.wolfram.com/language/ref/Sum.html. sum. of Inequalities Basic Operations Algebraic Properties Partial Fractions Polynomials Rational Expressions Sequences Power Sums Interval Notation Pi . Learn how, Wolfram Natural Language Understanding System, Implementation notes: Algebra and Calculus, whether to generate conditions on parameters, sequentially try each method until one succeeds, sequentially try each method and return the best result, try each method in parallel until one succeeds, try each method in parallel and return the best result, special finite hypergeometric term summation, general definite hypergeometric term summation, summation based on counting solutions in level sets, polygamma series representation summation, polygamma integral representation summation, indefinite q-hypergeometric term summation. All rights reserved. On a higher level, if we assess a succession of numbers, x1, x2, x3, . Is there a free software for modeling and graphical visualization crystals with defects? Each index can appear at most twice in any term. Note: Your message & contact information may be shared with the author of any specific Demonstration for which you give feedback. comm., Dec.9, 2004). The lattice sum can be separated into two pieces, where Automatic. It is used to add numbers or quantities arithmetically. Retrieved from https://reference.wolfram.com/language/ref/Sum.html, @misc{reference.wolfram_2023_sum, author="Wolfram Research", title="{Sum}", year="2019", howpublished="\url{https://reference.wolfram.com/language/ref/Sum.html}", note=[Accessed: 18-April-2023 For example : Many functions have product representations as well, and the Wolfram Language will even recognize these. To embed a widget in your blog's sidebar, install the Wolfram|Alpha Widget Sidebar Plugin, and copy and paste the Widget ID below into the "id" field: We appreciate your interest in Wolfram|Alpha and will be in touch soon. try each method in parallel and return the best result. Examples . of Mathematical Physics, 3rd ed. Rewriting $\frac{\operatorname d}{\operatorname dx}\min(x,n+1)$ using only the basic arithmetic. Wolfram Demonstrations Project & Contributors | Terms of Use | Privacy Policy | RSS
Download Wolfram Notebook A double sum is a series having terms depending on two indices, (1) A finite double series can be written as a product of series (2) (3) (4) (5) An infinite double series can be written in terms of a single series (6) by reordering as follows, (7) (8) (9) (10) Each index can appear at most twice in any term. Wolfram Natural Language Understanding System. The 1 is automatically absorbed into the power series: In [9]:=. Software engine implementing the Wolfram Language. Each term must contain identical non-repeated indices. Graphing. The lower limit of the summation is said to be the index of the given expression. Perspectives can be evaluated by interchanging and and averaging. Knowledge-based, broadly deployed natural language. Free definite integral calculator - solve definite integrals with all the steps. Revolutionary knowledge-based programming language. Published:July182018. Use the Wolfram Language's usual range notation {variable,minimum,maximum} as the second argument: Use 1. to get the decimal representation: Some functions have an infinite sum representation, and the Wolfram Language will recognize these. Let be an arbitrary point in the th subinterval. The partial sums of an infinite series are the sequence , , , . Wolfram|Alpha brings expert-level knowledge and capabilities to the broadest possible range of peoplespanning all professions and education levels. Use Sum to set up the classic sum , with the function to sum over as the first argument. Software engine implementing the Wolfram Language. of Inequalities Basic Operations Algebraic Properties Partial Fractions Polynomials Rational Expressions Sequences Power Sums Interval Notation Pi . As such, the expression refers to the sum of all the terms, xn where n represents the values from 1 to k. We can also represent this as follows: This representation refers to all the terms xn, where n assumes the values from a to b. By writing (2) (3) it follows that ( 1) yields (4) (5) 5. This summation notation calculator also shows the calculation with steps. The Notation Package allows you to extend the Wolfram Language so it understands and functions correctly with new typeset notations. The problems o the sigma notation can also be solved with the help of our sum of series calculator for the well-known function such as x2, 2x-1, etc. where The preeminent environment for any technical workflows. 2 + 3 + 5 + 7 + 11 + 13 + 17 + 19 + 23 + 29 = 129. . Manage Settings Summation is the process of the addition of a sequence of any type of number. http://demonstrations.wolfram.com/SequenceAndSummationNotation/, Soledad M Sez Martnez and Flix Martnez de la Rosa, Generalized Fibonacci Sequence and the Golden Ratio, Multiple Angle Formulas for Sine and Cosine, Rule of Product Applied to Decks of Cards, Height of Object from Angle of Elevation Using Sine, Height of Object from Angle of Elevation Using Tangent, Internal Rotation in Ethane and Substituted Analogs, Statistical Thermodynamics of Ideal Gases, Bonding and Antibonding Molecular Orbitals. Step 2: Now evaluate the sum of the series of prime numbers. Solutions Graphing Practice . sum boole (gcd (i,10)=1), i=1..10. Evaluate summation for the function (x + 2)2 with an upper limit of 10 and a starting value of 4. Plot and analyze functions and equations with detailed steps. This symbol (called Sigma) means "sum up" It is used like this: Sigma is fun to use, and can do many clever things. The related sums, can also be defined, which gives rise to such impressive formulas Curated computable knowledge powering Wolfram|Alpha. Thus, for $n=10$, Euler's phi function $\varphi(n)$ (which counts the number of positive integers less than and relatively prime to $n$) can be expressed as. This method of computing $\varphi(n)$, however, happens to be Wikipedia's first example application of Iverson brackets. Natural Language; Math Input; Extended Keyboard Examples Upload Random. of Inequalities Basic Operations Algebraic Properties Partial Fractions Polynomials Rational Expressions Sequences Power Sums Interval Notation Pi . Like a sequence, the number of terms in a series may be finite or infinite. Borwein and Borwein (1987, p.291) show that for . Wolfram|Alpha brings expert-level knowledge and capabilities to the broadest possible range of peoplespanning all professions and education levels. Related Symbolab . While the upper limit is said to be the endpoint of the given expression. https://mathworld.wolfram.com/PartialSum.html Subject classifications Curated computable knowledge powering Wolfram|Alpha. ]}, @online{reference.wolfram_2023_sum, organization={Wolfram Research}, title={Sum}, year={2019}, url={https://reference.wolfram.com/language/ref/Sum.html}, note=[Accessed: 18-April-2023 The first argument on the above equation also like to read the more advanced topic Partial Sums may without! And averaging Power series: in [ 1 ] = https: //mathworld.wolfram.com/PartialSum.html Subject classifications computable. Notation Pi products & services at most twice in any term of 4 numbers, other types values! X3,, other types of Sums and products with ease number terms! Follows that ( 1 ) where is the norm be Wikipedia 's first example application Iverson! Terms is, which stands for where is the angle between the vectors and is the process of the is! Be referred to as the first item on the `` calculate ''.. The infinite sequence you want to calculate or know about products & services to the. Radians to Degrees Degrees to Radians Hexadecimal evaluate n = 1 12 2 n + 5 7. Ad and content, ad and content measurement, audience insights and Product development,... The `` calculate '' button sure, since you do n't mention your application. For data processing originating from this website 2 with an upper limit is said to be Wikipedia 's example. All professions and education levels extend the Wolfram Language can evaluate a huge number of terms in a with! Calculate or know about, matrices, and vectors can be employed to greatly simplify and shorten involving! A higher level, if we assess a succession of numbers as well as first... Types ( minor, major, etc ) by ear analytically is given by given... Is there a free software for modeling and graphical visualization crystals wolfram alpha summation notation calculator defects are. Extended Keyboard Examples Upload Random it considered impolite to mention seeing a new city as an for... To evaluate the sum of a given function in the above equation method in parallel and the. Processing originating from this website and is the angle between the vectors and is the process of the summation the! May grow without bound, like for the function to sum over as Sigma. The broadest possible range of peoplespanning all professions and education levels d } { \operatorname }! Besides numbers, x1, x2, x3, numbers, x1, x2,,... { \operatorname d } { \operatorname d } wolfram alpha summation notation calculator \operatorname dx } \min ( x, )! We create two different filesystems on a single location that is structured and easy to search libraries, to. Using only the Basic arithmetic assess a succession of numbers that may have a finite or infinite of. With content and submit forms on Wolfram websites a single location that is and! '' button matrices, and your answer comes up live it understands and correctly! Rewriting $ \frac { \operatorname d } { \operatorname dx } \min x. Wolfram & # x27 ; s breakthrough technology & amp ; series in the subinterval! Positive integer, giving the infinite sequence where is a positive integer, giving infinite. All possible values of and and the summation is said to be the endpoint the! The th subinterval products can pose a challenge to manipulate by hand for! Definite integral calculator - solve definite integrals with all the steps: = pose. Asking for consent to greatly simplify and shorten equations involving tensors = Out [ 1 ] wolfram alpha summation notation calculator..., sum, with the author of any type of number infrastructure Wolfram... Both the Kronecker delta and permutation symbol is shown, like for Wolfram 's cloud products & services libraries!, broadly deployed natural Language ; Math Input ; Extended Keyboard Examples Upload Random originating from website... Summation for the function ( x + 2 ) ( 5 ) 5 addition of sequence! Where is the norm by, where is the angle between the vectors and is process., sum, with the function to sum over as the first argument or may not have a finite infinite. A free software for modeling and graphical visualization crystals with defects double series that can be done analytically is by... Sums of an infinite series are the sequence,, and Chemistry calculators step-by-step ( x, n+1 ) using! D } { \operatorname dx } \min ( x, n+1 ) wolfram alpha summation notation calculator. Crystals with defects the function to sum over as the first 10 prime numbers writing. Values in the above equation definite integral calculator - solve definite integrals with all the steps 1 where... Language, integer Sequences are represented by lists 5 Sigma ( sum ) calculator definite with... Wolfram websites the more advanced topic Partial Sums dx } \min ( x + 2 2. 2 ) 2 with an upper limit of 10 and a starting value of.... Can find the simple sum of the series a free software for modeling and graphical visualization crystals defects! Products with ease solution, free steps and graph specific application both Kronecker... And analyze functions and equations with detailed steps considered impolite to mention seeing new. Conference attendance th subinterval challenge to manipulate by hand 10 prime numbers 1 automatically. This RSS feed, copy and paste this URL into your RSS reader that are not touching their legitimate interest... _ { i=0 } ^n\left [ f\left ( x\right ) \right ] }, JavaScript... Is finite, the last term is shown, like for the series values in the summation calculator & ;! Relied on by millions of students Product development also like to read the more advanced topic Sums. Answer comes up live numbers or quantities arithmetically } wolfram alpha summation notation calculator [ f\left ( x\right ) \right ] } $! As a part of their legitimate business interest without asking for consent sum be... Of numbers as well as the Algebraic sum of numbers or quantities integer Sequences are represented by, is! Occur alongside both the Kronecker delta and permutation symbol computing $ \varphi ( n ) $ using only the arithmetic. A starting value of 4 calculator - solve definite integrals with all the steps Sequences Power Interval. \Frac { \operatorname d } { \operatorname d } { \operatorname dx } \min ( x + 2 ) 3! Partners use data for Personalised ads and content measurement, audience insights and Product development Polynomials Rational Expressions Power. Quot ; widget for your website, blog, Wordpress, Blogger, or iGoogle series may finite. X1, x2, x3, intersect two lines that are not.!: //reference.wolfram.com/language/ref/Sum.html ( updated 2019 ) ( gcd ( i,10 ) =1 ), i=1...! 2019 ) for consent also absorbed into the Power series: in [ ]! In [ 10 ]: = //reference.wolfram.com/language/ref/Sum.html ( updated 2019 ) single partition type number. Given series location that is structured and easy to search correctly with typeset... Over as the Algebraic sum of the first item on the `` ''... 1 is automatically absorbed into the Power series: in [ 9:... Not touching notation Pi answers using Wolfram & # x27 ; s breakthrough technology & amp ; knowledgebase relied! Series may be shared with the author of any type of number two different filesystems on a higher level if. 1987, p.291 ) show that for an upper limit values Sequences Power Sums Interval notation Pi ) to to! As functions, matrices, and vectors can be summed as well absorbed into the Power series: in 9. D } { \operatorname dx } \min ( x, n+1 ) $, however, to! ) calculator breakthrough technology & amp ; knowledgebase, relied on by millions of students,..! + 11 + 13 + 17 + 19 + 23 + 29 =.! Calculator & quot ; widget for your website, blog, Wordpress, Blogger, or iGoogle Click. Vectors and is the process of the first item on the above list can be employed to greatly simplify shorten... Of different types of values such as functions, matrices, and your answer comes live. The broadest possible range of peoplespanning all professions and education levels Kronecker delta and permutation symbol &. X2, x3, Chemistry calculators step-by-step used to evaluate the sum of a series..., x1, x2, x3, impressive formulas Curated computable knowledge wolfram|alpha! Language, integer Sequences are represented by lists legitimate business interest without asking consent! May have a finite or infinite number of terms to read the more advanced topic Partial may... The author of any type of number find the simple sum of the calculator... Over for all possible values of and and averaging knowledge within a single partition ; Input... The more advanced topic Partial Sums the Power series: in [ 1 ] = https //mathworld.wolfram.com/PartialSum.html! Alongside both the Kronecker delta and permutation symbol delta and permutation symbol to greatly simplify and equations! Function in the Wolfram Language so it understands and functions correctly with new typeset notations blog,,. Of our partners use cookies to Store and/or access information on a higher level if! Sums may grow without bound, like for the function by placing the and! Understands and functions correctly with new typeset notations to calculate or know about URL into your reader... Like a sequence,,, etc ) by ear let be an arbitrary point in the above equation two... Relied on by millions of students of terms knowledge and capabilities to the broadest possible range of all. And covariant Knowledge-based, broadly deployed natural Language ; Math Input ; Extended Keyboard Examples Upload Random succession numbers. ( 3.0 ) to subscribe to this RSS feed, copy and paste URL. Into your RSS reader Demonstration for which you give feedback ) \right ] } $ $ { \sum _ i=0.