Given the identity
$\displaystyle \sum_{i=0}^{n} \binom{k-1+i}{k-1} = \binom{n+k}{k}$
Need to give a combinatorial proof by interpreting the parts in terms of compositions of integers
(neither by induction nor using subsets)
Please, help!
Given the identity
$\displaystyle \sum_{i=0}^{n} \binom{k-1+i}{k-1} = \binom{n+k}{k}$
Need to give a combinatorial proof by interpreting the parts in terms of compositions of integers
(neither by induction nor using subsets)
Please, help!