Calculate number of solutions for $\sum_{i=1}^k i\cdot x_i = n$
106896
Number of solutions of $x_1+2x_2+\cdots+kx_k=n$?
140763
How to prove that $\sum_{n=1}^{2012} \frac{1}{x_n} = 1 $ has finitely many solutions for positive integer $x_i$?
98933
Calculating the sum of $f(x) = \sum_{n=0}^{\infty} {n \cdot 2^n \cdot x^n}$
57330
Find the number of solutions of $\sin x+2 \sin 2x- \sin 3x=3$
57986
Sum of products of combinatorials
68848
How to simplify $\sum_{k=1}^nk\cdot k!$
6539
Prove $\sum_{i=1}^n i! \cdot i = (n+1)! - 1$?
92704
Prove that $\sum_{k=1}^{n}k\binom{n}{k}=n\cdot2^{n-1}$
70248
Closed-form expression for $\sum_{k=0}^n\binom{n}kk^p$ for integers $n,\,p$
95494
Number of solutions of an arithmetic function's equation
3199
Number of positive integral solution of product $x_{1} \cdot x_{2} \cdot x_{3}\cdot x_{4}\cdot x_{5}=1050$ is
124135
A general formula for $\sum (k-1)(k-2)(k-3)$?
146491
Number of solutions of $x_1+x_2+\dots+x_k=n$ with $x_i\le r$
26081
What will be total number of solutions of $a+b+c = n$?
118024
Simplify the expression $\binom{n}{0}+\binom{n+1}{1}+\binom{n+2}{2}+\cdots +\binom{n+k}{k}$
134311
How to determine equation for $\sum_{k=1}^n k^3$
57549
Finding the sum $\sum_{k=1}^rk^2\binom {n-k}{r-k}$