Derive the formula for the sum
5080
How can we sum up $\sin$ and $\cos$ series when the angles are in arithmetic progression?
33986
Calculate $\sum_{n=1}^{\infty}(\frac{1}{2n}-\frac{1}{n+1}+\frac{1}{2n+4})$
93690
How to obtain the sum of the following series? $\sum_{n=1}^\infty{\frac{n^2}{2^n}}$
59208
How to explain the equation about summation?
113633
sum of series using mean value theorem
68116
How to derive this version of variance formula
85626
prove $\sum_{i=1}^{n}(x_i-\bar{x})^2\lt\sum_{i=1}^{n}(x_i-a)^2$
138313
How to sum $\sum_{n=1}^{\infty} \frac{1}{n^2 + a^2}$?
129860
Find a formula for this sequence (and prove it).
30518
Formula for $\sum_{k=1}^n \frac{1}{k(k+1)(k+2)}$?
4253
How to calculate: $\sum_{n=1}^{\infty} n a^n$
123820
Guess the formula for $\sum\frac 1{(4n-3)(4n+1)}$ and prove by induction
103347
combinatorial proof of summation
121554
Finding $\sum\frac{1}{2^n(n+1)}$
29170
Find the sum of the series $\sum \frac{1}{n(n+1)(n+2)}$
89698
Please help with $\sum\limits_{r=1}^{N}\frac{2r+3}{3^r(r+1)}$
8806
Summation of binomial coefficients