Summation from 0 to n of cos((k/n)2 pi)
9479
$\sum \cos$ when angles are in arithmetic progression
114418
A deduction from $x^n-1=(x^2-1)\prod_{k=1}^{(n-2)/2}[x^2-2x\cos{\frac{2k\pi}{n}}+1]$
127150
Finding general formula of $\sum_{i=0}^n i^2 \binom{n}{i}$
116722
Simplifying $\big(\sum_{i=0}^n\binom{k}{i}\binom{M-k}{n-i}\frac{k-i}{M-n}\big)/{\binom{M}{n}}$
138847
Tricky trigonometric sum evaluation
38741
Finding a general formula for summation
115433
Find the summation of given expression: $\sum_{k=1}^n k^3\binom nk$
70248
Closed-form expression for $\sum_{k=0}^n\binom{n}kk^p$ for integers $n,\,p$
7891
Sum of nth roots of unity
37007
Evaluating $\sum_{k=1}^{n} \frac{1}{k(k+1)}$
87479
Closed form for $\sum_{k=0}^{n-p}\binom{n}{k}\binom{n}{p+k}$
150928
Summation of a trigonometric series - $\frac{\sin n}{n}$
30518
Formula for $\sum_{k=1}^n \frac{1}{k(k+1)(k+2)}$?
69045
Solving this summation: $\sum_{i=1}^k i\cdot2^i$
142985
Finding sum of series $\sum^{\infty}_{k=0}\frac{(k+1)(k+2)}{2^k}$
114414
Sum of $\sum_{k=1}^n\sin{k\theta}$
42736
Is there a closed form for $\sum_{k=0}^n \frac{x^k}{k!}$?