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2
votes
3answers
190 views

Sum with Levi-Civita

I'm trying to write the expression $$\sum_{\alpha,\beta = 1}^{4}\epsilon_{\mu \nu\alpha\beta}a^{\nu} b^{\alpha} c^{\beta}$$ in Mathematica, where $\epsilon$ is the Levi-Civita symbol and $a$, $b$, $c$ ...
0
votes
1answer
40 views

Collapsing summation

I am trying to write a command to collapse the sum of terms into an expression with summation. Something like ...
7
votes
2answers
173 views

sudden increase in timing when summing over 250 entries

Using math 9.0.1 on a MacBook Air, I see a sudden increase of Timing by a factor of thousands when I sum over 250 elements of a matrix rather than over 249. So for ...
1
vote
1answer
55 views

How would one minimize with respect to an unknown number of variables?

Say I had a function like the following: f[n_] := Sum[a + Subscript[b, k], {k, 0, n}] Such that ...
0
votes
2answers
74 views

How can I speed up this code?

There are 4 variables in this multiple sum, and only 2 are used. This question has the similar scenario as the previous one How can I speed up this code with multiple sum?, but the calculation ...
1
vote
1answer
63 views

Problem with infinite sum

I am facing a problem in evaluating infinite sums of the following form. As a first thing define the following function ...
1
vote
2answers
84 views

Problem evaluating a complicated integral

Apologies for stating my problem poorly in the first instance, thank you for the help in narrowing down the issue. Problem For those interested, it's for the exact unbiased inverse of the ...
1
vote
1answer
78 views

Symbolic evaluation of the sum of KroneckerDelta

I want to evaluate this simple expression $$ \sum_n f(n)\delta_{mn} = f(m) $$ using this: Sum[KroneckerDelta[m, n] f[n], {n, Infinity}] However Mathematica ...
0
votes
0answers
29 views

How to calculate this derivative? [duplicate]

Can Mathematica do the following simple calculation? $$F(x_0, x_1, x_2, ...) \equiv \sum_n x_n^2$$ I want to do the symbolic calculation: $$ \frac{\partial F}{\partial x_m} = \sum_n 2 x_n ...
3
votes
1answer
83 views

Collect terms in a sum

Suppose I have this expression ...
0
votes
2answers
72 views

How do I sum up p items in a sequence?

I have the following sequence list = {p1, p2, p3, p4 ....} I am summing up the p items as follows: p1 + p2 + 2*sqrt (p21*p2) = p12 p12 + p3 + 2*sqrt (p12*p3) = p123 p123 + p4 + 2*sqrt (p123*p4) = ...
0
votes
0answers
47 views

Expectation taking unusually long to evaluate

I am trying to evaluate an expectation, but it is taking an extremely long time although the expression itself should not be too complicated. My code is ...
1
vote
1answer
103 views

Compute symbolic Expectation of a summation

I am required to computed following Expectations : $E[\displaystyle\sum\limits_{i=1}^N \frac{X_{i}}{N}] = \bar{x}_{0}$ & $E[\displaystyle(\sum\limits_{i=1}^N \frac{X_{i}}{N})^2] = ...
1
vote
1answer
65 views

Simplify results further

I have an extremely long result in polynomial form following some matrix operations. However, given the symmetry of the problem, I can safely say that the solution will reduce much further than is ...
3
votes
1answer
30 views

Strange NSum behavior for slightly larger number of terms

For some sums, NSum gives me the result nicely for some number of terms, but if I add one more term, it suddenly becomes much slower. I haven't found the minimum example for which this can be ...
1
vote
2answers
94 views

Assign a Distribution to a group of symbolic variable [closed]

I'm looking to compute this Expectation : "i" represent a individual and h(i) is value. I would like the compute the Expected value of his value times the mean of the groups. Everything is unknown ...
5
votes
3answers
187 views

Numerical evaluation of a sum

I am trying to compute numerically NSum[(-1)^n/n^3, {n, 1, Infinity}]. Of course, using first Sum would work here, but often ...
3
votes
1answer
182 views

How can I speed up this code with multiple sum?

There are 4 variables in this multiple sum, therefore it may take a long time. I have run this program for 12 hours, but no result untill now. I want to know how to speed up this code. Any help or ...
2
votes
0answers
99 views

Computing a sum

I'm trying to make Mathematica compute this sum: Sum[(-1)^k (n - k)^2 Binomial[2 n, k], {k, 0, n}] As is, I get an awful formula: ...
0
votes
1answer
92 views

About doing an sum

I want to explain this summation to Mathematica, For $a >0$ define $n_u, n_d \in \mathbb{Z}$ such that if $\{ a \} \leq 0.5$ then $n_u = [a]-1$ and $n_d = - [a]$ and if $\{ a \} > 0.5$ then ...
4
votes
2answers
145 views

Solve a system of M equations without specifying M

This post has been edited heavily in response to the comments: my initial question was very confusing. I am trying to write my game-theoretic model in Wolfram Language. There is only one remaining ...
4
votes
1answer
122 views

Variable number of nested variable-range sums

I would like to express the following nested sum in Mathematica: $$ S(m,j,N) = \sum_{k_1=m+j-1}^{N-1} f(N,k_1) \sum_{k_2=m+j-2}^{k_1-1} f(k_1,k_2) \cdots \sum_{k_m=j}^{k_{m-1}-1} f(k_{m-1},k_m) $$ ...
1
vote
0answers
57 views

Summing a trig series

I am trying to sum the following expression: (Cos[(2 π m)/N]^2 Cos[(2 π n)/ N])/(2 (Cos[(2 m π)/N] - Cos[(2 n π)/N])) from ...
1
vote
2answers
107 views

Sum does not converge, but I think it should

Why does Mathematica return Sum::div: Sum does not converge. >> When I input Sum[Boole[!IntegerQ[x]], {x, 1, Infinity}] The sum is obviously 0.
6
votes
0answers
145 views

Incorrect evaluation for Thue-Morse signed harmonic series

I would like to evaluate $$s = 1 - \frac{1}{2} - \frac{1}{3} + \frac{1}{4} - \frac{1}{5} + \frac{1}{6}+\frac{1}{7}-\frac{1}{8} - ... + \frac{(-1)^{\textrm{binary digit sum}(n-1)}}{n} + ... $$ where ...
0
votes
2answers
94 views

What is wrong in my calculation with clebsch-gordan coefficients?

According to theory of angular momentum here must equal one. What's wrong? ...
2
votes
0answers
114 views

Faster Ways to compute recursive summation

It takes a long time to compute the summation below, and I'd like to know if there are some better ways to compute things faster. I have used $3$ ways to calculate, but they are very unsatisfactory. I ...
7
votes
6answers
666 views

Alternating sum

A frog is at the bottom of a 30 metre well. Each day it climbs 5 metres up the side, but it then slips back 3 metres each night. How long does it take to reach the top of the well? Is there an easier ...
0
votes
0answers
81 views

HypergeometricPFQ

I am trying to get a simple but relatively ugly result out of the following summation, however, mathematica gives me an expression which includes HypergeometricPFQ. Obviously, I am doing something ...
1
vote
1answer
80 views

Summation for a function having singularity

I need to do summation of this function with Mathematica. For[t=0,t<500,t++;Sum[-Q*Log[Q],{k,-Infinity,Infinity},{n,-Infinity,Infinity}]] Q= Q1+Q2+Q3 where ...
0
votes
0answers
56 views

Manipulating infinite series

If I type Sum[f[x],{x,m,Infinity}]-Sum[f[x],{x,m+3,Infinity}] I would like Mathematica to return something like ...
1
vote
1answer
77 views

How to assign Subscript[C, i] to a Sum?

What I want to show is: Plot3D[ Sum[1000*Subscript[C, i]^2/(1000*Subscript[C, i] - 600)^r, {i, 1, k}], {k, 1, 30}, {r, 0.1, 1.5}] And, I want the list of ...
1
vote
0answers
34 views

How do I define a tensor from another tensor with summations? [duplicate]

Let's say we have a rank 2 tensor $g_{ij}$. This is basically a list with a Depth of 2. Now I'd like to calculate another tensor ...
2
votes
1answer
113 views

Deriving least-squares equations in Mathematica

I define $Y = a + b*x + e$, and I want to find values for $a,b,$ by least squares, so I minimize $RSS = sum((Y_i - a - b*x_i)^2)$ I then take derivatives, ${d RSS \over da} = 0$ and ${d RSS \over db} ...
1
vote
1answer
114 views

How to define a summation with function calling itself?

I am new to Mathematica. I want to do this f(x)=summation f(t), summation is over t, where 1<=t<=x-1 and mod(x+1,t+1)=1, i.e. when x+1 is divided by t+1, remainder is 1 and f(1)=1. Should i use ...
-5
votes
1answer
186 views

How can I plot a function that is the sum of another function?

I plotted m[t], but actually what I want to plot is g[t], which is a summation of m[t] from ...
-3
votes
2answers
92 views

Find the value by using FindRoot command [closed]

The equation x^4-3 x^3 = cos(3x)+3 has two real solutions on the interval from -10 to 10. Lets call these two solutions r and s. Use Mathematica's FindRoot command to find r and s. Now let M equal the ...
0
votes
2answers
88 views

Sum equation with equation and get an equation

I am trying to get an equation from summing other equations but it doesn't result in a correct answer. Is there another way of doing this? ...
2
votes
0answers
73 views

Limit[Sum[(2*E*n)^w/(w^(n/2+w)), {w,2,n}],n->Infinity]

I would like to show that the following (and other similar formulae) tends to zero. Limit[Sum[(2*E*n)^w/(w^(n/2+w)), {w,2,n}],n->Infinity] What's the right ...
1
vote
5answers
93 views

Question about sum and list in a function

I have a list of this form: $ lst =\left\{\left\{q_1,x_1,y_1,z_1\right\},\left\{q_2,x_2,y_2,z_2\right\},\text{...},\left\{q_n,x_n,y_n,z_n\right\}\right\} $ I want to use this list in the function: ...
2
votes
2answers
116 views

How to exclude numbers in a series and still plot the graph? [duplicate]

I want to plot this: $\displaystyle\sum_{n=-{10}\atop n\ne \pm 1}^{10} \dfrac {4i(-1)^{n}n}{(n^2 - 1)^2}e^{inx}$ but have no idea how I can exclude the cases for when $ n = \pm 1 $. I don't wish to ...
0
votes
0answers
48 views

Need to take infinite sum of residues, is there a way to choose the order of operations for ReleaseHold?

I'm computing an infinite sum of residues. I want to do something like this: ...
3
votes
2answers
274 views

Incorrect value of infinite sum

Wolfram Alpha and Mathematica give an incorrect result (numerically) for the following infinite sum: ...
2
votes
2answers
190 views

Triple series - evaluation delayed

Trying to figure out if the infinite triple series has a nice closed form. It seems Mathematica is unable to help us here. Numerically, things remain the same, no response. Could you help? ...
1
vote
1answer
112 views

Module that finds the sum of digits of any given positive integer

How can I make a module that finds the sum of digits of any given positive integer? I use this command F[x_]:= Apply[ Plus, IntegerDigits[x] ] Is there another ...
4
votes
1answer
207 views

Summation with jump indices like 1,4,6,9?

I is easy to enter $ \sum_{s=1}^{n}k(s) $ But how can I enter $ \sum_{s=1,3}k(s) $ ? When I try it, Mathematica says ...
2
votes
2answers
112 views

Plot with sum and binomial command

A few days ago I asked about a problem with plotting a sum. You advise me to use Evaluate option, and that helped me very. But now I have a very similar problem, but i can't find the mistake. I have a ...
2
votes
1answer
136 views

Reproducing a Plot done with WolframAlpha [duplicate]

I have problem to draw in Mathematica a plot like this: Plot[{Sum[a^10*(-1)^(x-a), {a, 1, x}]}, {x, 1, 10}] The problem is that on the plot there is no graph. As ...
2
votes
1answer
82 views

Evaluating terms in series

I'm trying to evaluate a simple expression: Subscript[λ, n] = (2 n - 1) π/(2 L); And then sum it up: ...