How can I solve this sum? $\sum_{k=1}^{n}k2^{k-1}$
7063
How to compute the  formula $\sum  \limits_{r=1}^d r \cdot 2^r$?
124135
A general formula for $\sum (k-1)(k-2)(k-3)$?
39909
Getting a closed form from $\sum_{i=1}^{n-1} \sum_{j=i+1}^{n} \sum_{k=1}^{j} 1$
26446
Find the sum : $\displaystyle\sum_{i=0}^n \frac{2^i}{1+x^{2^{i}}}$
58247
Prove $\sum_{k=0}^n \binom{n+k}{k}=\binom{2n+1}{n}$
59252
Show $\sum_{k=0}^{m} \binom{n-k}{m-k}=\binom{n+1}{m}$
3798
Finding formula for sum $S_n = \sum_{i=1}^n i(i-1)$
57549
Finding the sum $\sum_{k=1}^rk^2\binom {n-k}{r-k}$
36083
If $k > 1$, then $\frac1{(k - 1)^2}-\frac1{(k + 1)^2}=\frac{4k}{(k^2 - 1)^2}$, hence simplify $\sum\limits_{k = 2}^n\frac k{(k^2 - 1)^2}$
129801
Finding a closed form for $\sum^{n}_{k=1} \frac{k}{(k+1)!} $
106552
Find the sum of $\sum \frac{1}{k^2 - a^2}$ when $0<a<1$
115433
Find the summation of given expression: $\sum_{k=1}^n k^3\binom nk$
37771
Sum of a power series $n x^n$
120976
Proving $\sum_{k=0}^{n}k{n\choose k}^2 = n{2n-1 \choose n-1} $
136580
Proving $\sum_{k=0}^n\binom{2n}{2k} = 2^{2n-1}$
19581
$\sum_{k=0}^n (-1)^k \binom{n}{k}^2$ and $\sum_{k=0}^n k \binom{n}{k}^2$
138542
Evaluating sums question $\sum_{k=2}^n \frac{1}{k^2-1}$