10 MH
10.0.1 Binomial coefficient
The number of unordered samples of y objects selected from n objects without replacement is
\[ {n \choose y} = \frac{n \times (n-1) \times (n-y-1)}{y!}) \\ = \frac{[n \times (n-1) \times (n-y+1)](n-1)!}{(n-1)!y!} \\ = \frac{n!}{(n-1)!y!}\]