Combinatorial Argument for $i{n \choose i} = n {n-1 \choose i-1}$
44484
Combinatorial identity $i{n \choose i } =n {n-1 \choose i - 1}$
84394
Choice function for a collection of nonempty subsets of $\{0,1\}^\omega$
6204
How many permutations of $\{1, \ldots, n\}$ exist such that none of them contain $(i, i+1)$ (as a sequence) for $i \in {1,...,(n-1)}$?
71564
Combinatorial proof of identity involving central binomial coefficients
107021
Finding a combinatorial argument for an interesting identity: $\sum_k \binom nk \binom{m+k}n = \sum_i \binom ni \binom mi 2^i$
47799
Show that the number or $r$ combinations of $X$ which contain no consecutive integers is given by $\binom{n-r+1}{r}$
74730
Combinatorial Proof of ${{n}\choose{k}} {{k}\choose{j}} = {{n}\choose{j}} {{n-j}\choose{k-j}}$
36388
How to derive this Combinatorial identity
75910
Combinatorial Proof of Combinatorial Identity involving $(-1)^k \binom {n-1}{k}$
1139
Combinatorial proof of $\sum_{j=0}^{k} \binom{n}{j} = \sum_{j=0}^k \binom{n-1-j}{k-j}2^j$
9971
enumerative combinatorics,In how many ways (as a function of n) can one choose a composition α α of n
925
Prove that $F_n={n-1 \choose 0 }+{n-2 \choose 1 }+{n-3 \choose 2 }+\ldots$ where $F(n)$ is the $n$-th fibonacci number
70327
the numer of partial function between two sets in combinatoric way
7083
Alternating sum of binomial coefficients: given $n \in \mathbb N$, prove $\sum^n_{k=0}(-1)^k {n \choose k} = 0$
139398
Distribution of $n\choose x$
59831
How to relate combinatorial proof to bipartite graphs?
56828
A combinatorial proof that the alternating sum of binomial coefficients is zero