The arrangement of m in n numbers is Anm(n is subscript, m is superscript), the combination number of m in n numbers is Cnm(n is subscript, m is superscript), anm = n (n-1) (n-2) ... (n-m+1).

Cnm = n (n-1) ... (n-m+1)/(1× 2× 3× ... × m)