Chu-Vandermonde-like combinatorial identity
7143
Identity for convolution of central binomial coefficients: $\sum\limits_{k=0}^n \binom{2k}{k}\binom{2(n-k)}{n-k}=2^{2n}$
109649
idempotents acting as local identities
116356
Combinatorial proof of $2 \cdot 3^0 + 2 \cdot 3^1 + 2 \cdot 3^2 + \cdots 2 \cdot 3^{n-1} = 3^n-1$
42763
How to prove Vandermonde's Identity: $\sum_{k=0}^{n}\binom{R}{k}\binom{M}{n-k}=\binom{R+M}{n}$?
125174
Combinatorial intuition of identity
29828
Combinatorial proof of $\sum^{n}_{i=1}\binom{n}{i}i=n2^{n-1}$.
62175
A general formula for $n$ distinguishable arrangements of length $\ell$ of a sequence of a given size?
158508
Combinatorial Proof for Binomial Identity: $\sum_{k = 0}^n \binom{k}{p} = \binom{n+1}{p+1}$
129304
Alternative combinatorial proof for $\sum\limits_{r=0}^n\binom{n}{r}\binom{m+r}{n}=\sum\limits_{r=0}^n\binom{n}{r}\binom{m}{r}2^r$
140140
An identity which applies to all of the natural numbers
149686
Combinatorics and trigonometry identity
31076
Roots of unity filter, identity involving $\sum_{k \ge 0} \binom{n}{3k}$
19571
Combinatorial proof for $\sum_{k = 0}^n \binom {r+k} k = \binom {r + n + 1} n$
71564
Combinatorial proof of identity involving central binomial coefficients
24212
proving how many permutations exist.
52083
Vandermonde determinant for order 4
14836
A polynomial sequence