- distributing identical balls into a set of distinct boxes empty allowed:
n = number of distinct boxes, m = number of identical balls
$\binom{n+m-1}{m}$ so 5 balls, 3 boxes would result in $\binom{7}{5}$
- distributing identical balls into a set of distinct boxes with no empty boxes
$\binom{m-1}{n-1}$
- set of distinct balls into a set of distinct boxes
T(m,n)