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# Questions tagged [summation]

Questions using the Sum command, especially for series and other algebraic objects, and related functions such as SumConvergence

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### Not getting a solution to my maximization problem

I want to solve the following problem: For $0.5<q<1$, $q<r<1$, $0\leq n$, $0\leq n_1<=\lfloor{n/2}\rfloor$, and $n_1,n\in\mathbb{N}$ calculate $\arg max_{n_1} S(q,r,n,n_1)$ as a ...
41 views

### Performance Tuning: Construction of Matrix with Summations

I am trying to solve an eigenvalue problem of a large matrix. The issue is that it takes too much time to construct this large matrix. This is the code that I built: ...
52 views

### How do I make this summation work faster?

Is there any way to make this summation be faster? I previously had spherical harmonics integration which was taking forever to run How can I do a faster integration? Using math, I tried to use ...
753 views

### How to optimize Mathematica code that depends on eigenvalues of big matrices and big sums?

I've been using Mathematica recently to generate some plots of a few functions. I've been able to get it right after a few questions here. The resulting code, which works, is this: ...
111 views

### What am I doing wrong when trying to plot this function?

I'm trying to reproduce the computations of this paper and I'm running into some troubles because I'm rather new to Mathematica. In the paper's page 4, in figure 2 the authors show a plot of a ...
67 views

### Evaluating a summation while suppressing zero raised to a negative power

I want to compute the following multiple summation. ...
63 views

### Why does Sum[Length[Divisors[a]], {a, 1 ,x}] return x?

I am summing the number of divisors and I am getting the strange answer below even where there is no input to this function. ...
102 views

### How to sum over the variable in partial derivative operator?

I need to use the partial derivative operator in Wolfram Mathematica within a summation, specifically to define the D'Alembertian operator of scalar fields. I am having trouble summing over the D ...
33 views

### Evaluation of Extract and use the result in a Sum

I am experiencing a problem in the evaluation of a sum. I hope that someone can help me, I am not an expert Mathematica programmer. I'm posting just the portion of code that gives problems, I know ...
112 views

### Strange result with an indefinite double sum

Bug introduced in V10.0.2 or earlier and persists through V11.3 (Simplified version - courtesy Lukas Lang - reported [CASE:4208776]) I try to compute ...
212 views

### If and summation: why do I have the index of the summation in the final result?

Consider the following code: Sum[If[b != 0, a[m], 0], {m, 1, 4}] (* 4 If[b != 0, a[m], 0] *) Why does it return me a[m]? m ...
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### Rearrange Summation and change duplicated indices

I try to transform $$\left(\sum _{j=1}^J A(j)\right) \sum _{j=1}^J \sum _{k=1}^K B(j,k)$$ to $$\sum _{j=1}^J \sum _{k=1}^K \sum _{j_{2}=1}^J A(j_{2})B(j,k)$$ The rule would add subscript to ...
44 views

### Sums of binomial expressions returns different and sometimes indeterminate expressions

A problem that I encountered multiple times when taking sums over expressions involving binomials, factorials, etc. is that Mathematica (version 11.2) returns indeterminate expressions when it should ...
134 views

### How to extract a coefficient from a sum

Let us consider a sum of specified functions multiplied by coefficients, for example f[x_]:= Sum[Exp[j*x]*p[j],{j,1,n}] I want to extract the coefficient ...
83 views

### Derivative of sum of elements of array [closed]

I try to get derivative of sum of an array with respect to an element of the array. $$s = \sum_{i = 1}^{3}A_{i, 1}$$ Evaluate $\frac{\partial s}{\partial A_{1,1}}$ Below is the code. ...
491 views

### Find asymptotics of $\sum\limits_{i=0}^{n/3} 2^i \binom{n-i-1}{\frac{2n}{3}-1}$

I have an expression 2^n / Sum[ 2^i Binomial[ n - i - 1, 2n/3 - 1], { i, 0, n/3}] ...
85 views

### Summations of Lists

I'm trying to find how many numbers between 1 and 1000, which are not either prime or the sum of successive primes. I've managed to create the list of all the primes between 1 and 1000: ...
784 views

### Compile nested Sums

I want to compile an expressions that contains nested Sum-expressions. A simple example that gives me problems is: ...
61 views

### NSum: Summand (or its derivative) is not numerical at point

I am experiencing a problem in evaluating the maximum of a function that is defined as a sum ...
374 views