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Questions tagged [summation]

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Questions about evaluating summations, especially finite summations. For infinite series, please consider the (sequences-and-series) tag instead.

16,061 questions
0 votes 0 answers 7 views

Last number in an upwards addition triangle, given the length of the last row.

In the lowest row the numbers 1 to n are written, then rows above consists of the sums of neighboring elements of the row below it (like in Pascal's triangle) until in the highest row only one number ... user avatar user3284214
  • 1
0 votes 0 answers 10 views

Closed form for $\sum_{k=0}^{n-1} \sin(m\theta_k)(\pi-\theta_k)$

In the process to compute $\int_0^{+\infty} \frac{t^{m-1}}{1+t^{2n}}{\rm d}t$ (see this thread), I got stuck on this sum : $$S_{m,n} = \sum_{k=0}^{n-1} \sin(m\theta_k)(\pi-\theta_k)$$ where $m$ and $n$... user avatar Nicolas FRANCOIS
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-1 votes 0 answers 30 views

Sum to infinity. [closed]

Could someone please explain how this sum is calculated? $$\sum_{n=0}^{\infty} \frac{a^n e^{(-a)}}{n!} = 1$$ Thanks Edit: $$=e^{-a}\sum_{n=0}^{\infty} \frac{a^n }{n!}=e^{-a}e^{a}=1$$ user avatar 0xFun
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0 votes 1 answer 44 views

How to correctly write down a summation used in a simulation

I am unclear on how to mathematically write a summation that is used in my simulation. I am trying to calculate the fluorescence for a slab with ends of -L and +L. There are currently 200 slices ... user avatar rdemyan
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1 vote 0 answers 29 views

Relating $\sum_{k=1}^N a_k^2 e^{\frac{2\pi i}{N}k}$ to $(\;\sum_{k=1}^N a_k e^{\frac{2\pi i}{N}k}\;)^2$

Consider the following expression $$ \sum_{k=1}^N a_k^2 e^{\frac{2\pi i}{N}k}\tag{1} $$ where $i$ is the imaginary number. How may I relate it to the following expression $$ \left(\sum_{k=1}^N a_k e^{\... user avatar sam wolfe
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0 votes 2 answers 39 views

write the given summation in terms of $x^n$ instead of $x^{3n}$

I have $\sum_{n\geq0}(2n)x^{3n} =0+2x^3+4x^6+6x^9+...$ , but i want to write this summation in terms of $x^n$ instead of $x^{3n}$ .How can i do it ? I thought that if i can write $n/3$ in place of $n'... user avatar user1066985 1 vote 0 answers 34 views

Sum of binomial coefficients for a specific sum

I am trying to find the eigenvalues of a matrix, and the degeneracy of each eigenvalue is given by the following expression: \begin{equation} deg(2l)=4\sum_{\substack{\{0\leqslant 2i,2k \leqslant L^2:\... user avatar MarcPN
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0 votes 0 answers 9 views

Negative log-likelihood of Gaussian distributions

In a paper about collective outlier detection, I found the following penalized cost formula. $$ \sum \limits_{t\notin \cup \left[{\tilde{s}}_i+1,{\tilde{e}}_i\right]}\mathcal{C}\left({\mathbf{x}}_t,{\... user avatar lafinur
  • 1,368
1 vote 2 answers 64 views

Product of $n$ terms of sequence where the $n^{th}$ term is of the form $(x^{a^n}+1)$

While practicing from a book I found a product in the form $$(x^{a^1}+1)\cdot(x^{a^2}+1)\cdot(x^{a^3}+1)\cdot(x^{a^4}+1)$$ and was immediately curious if I could a formula to solve the product for $n$ ... user avatar Samar Sidhu
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0 votes 0 answers 21 views

How to switch from continuous to discrete formulation (integral to sum) in a specific case?

in the paper "Economic conditions and the popularity of parties: a survey" Kirchgaessner (1986) transforms a utility function from continuous to discrete. I get the intuition and the meaning,... user avatar george1994
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0 votes 2 answers 76 views

Evaluating $\sum_{k=0}^{\infty}\frac{1}{2k-1}$

$\sum_{k=0}^{\infty}\frac{1}{2k-1}$ is a convergent series. Is there some way to evaluate $\sum_{k=0}^{\infty}\frac{1}{2k-1}$ This does not look like arithmetic or geometric series to me. Please help user avatar Orpheus
  • 810
4 votes 1 answer 36 views

Infinite symmetrical matrix sum (discrete Lyapunov equation)

I have 2 symmetrical matrices ($A$ and $B$) and I am looking to find the sum $S$: $$S=A+BAB+B^2AB^2+\ldots$$ Or in summation format: $$S=\sum_{i=0}^\infty B^iAB^i$$ We know that the absolute magnitude ... user avatar PC1
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1 vote 0 answers 18 views

How to derive the swap rate for a market maker in the given example?

I'm struggling with a section of Financial Mathematics for Actuaries, Second Edition, by Wai-Sum Chan and Yiu-Kuen Tse. Any help would be appreciated! Can't quite seem to figure this one out. I think ... user avatar David Loungani
  • 137
2 votes 1 answer 70 views

Closed form of $\sum_{k=1}^\infty\frac{k^nB_k}{k!}$

I developed the following: Consider $$\frac{t}{e^t-1}=\sum_{k=0}^\infty\frac{B_k}{k!}t^k,$$ where $B_k$ are the Bernoulli numbers, then $$\frac{e^t}{e^{e^t}-1}=\sum_{k=0}^\infty\frac{B_k}{k!}e^{tk}=\... user avatar gone
  • 9,883
-5 votes 1 answer 44 views

Prove by using binomial theorem on $(x-1)^n$ the following [closed]

Prove by using binomial theorem on $(x-1)^n$ the following: $$\sum_{k=0}^{n-1}(-1)^k(n-k)C^k_n=0$$ user avatar Mo2edmatic
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