Counting arguments question about sums of binomial coefficients
29828
Combinatorial proof of $\sum^{n}_{i=1}\binom{n}{i}i=n2^{n-1}$.
27141
Combinatorics identity question
45862
Nested sum of binomial coefficient in closed form
64803
Counting two ways, $\sum \binom{n}{k} \binom{m}{n-k} = \binom{n+m}{n}$
126587
Divisiblity of binomial coefficients
143945
Summation of combination of binomial coefficient
107810
Induction with Binomial Coefficients
61270
Binomial Theorem Sum
152084
Binomial-Theorem proof
59638
How to prove this result on binomial coefficients?
143365
Is $\sum_{i=1}^{n-1}i=\binom{n}{2}$?
19571
Combinatorial proof for $\sum_{k = 0}^n \binom {r+k} k = \binom {r + n + 1} n$
144571
A conjecture including binomial coefficients
57986
Sum of products of combinatorials
109599
A finite sum involving the binomial coefficients and the harmonic numbers
107021
Finding a combinatorial argument for an interesting identity: $\sum_k \binom nk \binom{m+k}n = \sum_i \binom ni \binom mi 2^i$
139842
Seeking a combinatorial proof $\sum\limits _{k=0}^n (n-2k)^2\binom{n}{k}=n\times 2^n$