Calculating $\sum_{k=1}^nk(k!)$ combinatorially
36436
Proving $\sum_{k=1}^n k k!=(n+1)!-1$
34299
Combinatorial proof of $\sum_{k=0}^n k \cdot k! = (n+1)! -1$
46132
Combinatorial interpretation for the identity $\sum\limits_i\binom{m}{i}\binom{n}{j-i}=\binom{m+n}{j}$?
49066
Give the combinatorial proof of the identity $\sum\limits_{i=0}^{n} \binom{k-1+i}{k-1} = \binom{n+k}{k}$
30338
How to prove that $\sum_{k=0}^n \binom nk k^2=2^{n-2}(n^2+n)$
89552
proving combinatorics identity - $\sum_{k=0}^m{n-k \choose m-k}={n+1 \choose m}$
140877
Evaluate the sum $\sum_{k=1}^n {n \choose k-1} {n \choose k}$
75227
If $S=\{1,2,\dots,n\}$ and $P_n(k)$ be the number of permutations of $S$ having $k$ fixed points, then $\sum_{k=0}^nk.P_{n}(k)=n!$
68308
A (probably trivial) induction problem: $\sum_2^nk^{-2}\lt1$
74887
Combinatorial proof of the identity ${n+1\choose k+1}={k\choose k}+{k+1\choose k}+...+{n-1\choose k}+{n\choose k}$
99868
Sum(Partition(Binary String)) = $2^k$
129801
Finding a closed form for $\sum^{n}_{k=1} \frac{k}{(k+1)!} $
65983
Combinatorial proof of binomial coefficient summation identity
65672
Proof of the summation $n!=\sum_{k=0}^n \binom{n}{k}(n-k+1)^n(-1)^k$?
92704
Prove that $\sum_{k=1}^{n}k\binom{n}{k}=n\cdot2^{n-1}$
99453
Sum of $k$-th powers
147766
Sum of Permutations from 0 to n