How to find $\sum_{k=1}^{n}{3^kk}$
562
Formula for calculating $\sum_{n=0}^{m}nr^n$
21000
Calculating $\sum_{k=1}^nk(k!)$ combinatorially
37771
Sum of a power series $n x^n$
151085
Simplify the sum $ \sum_{i=0}^{k}(-1)^i i \binom{n}{i} \binom{n}{k-i}$
121554
Finding $\sum\frac{1}{2^n(n+1)}$
141978
How to find the infinite sum
148442
Show that the sum $\sum_{k = 0}^n 2^k \binom{n}{k}$ is equal to $3^n$
13236
Proving equality - a sum including binomial coefficient $\sum_{k=1}^{n}k{n \choose k}2^{n-k}=n3^{n-1}$
7302
$\sum k! = 1! +2! +3! + \cdots + n!$ ,is there a generic formula for this?
28027
Find $\sum_{k=0}^{n}4^k \binom{n}{k}$
44328
Prove that $\sum_{k=1} ^ n k^{-1} = \ln(n) + O(1)$
140877
Evaluate the sum $\sum_{k=1}^n {n \choose k-1} {n \choose k}$
36361
How to calculate the summation $(\sum_{p = k}^{n} \binom{n}{p}) / 2^n$ quickly?
99453
Sum of $k$-th powers
89367
Calculate $ S =\sum_{k=1}^n\frac {1}{k(k+1)(k+2)}. $
126105
Compute $\sum_{k=1}^{n} \frac 1 {k(k + 1)} $
129801
Finding a closed form for $\sum^{n}_{k=1} \frac{k}{(k+1)!} $