a(n) = binomial(n-1,2)*n^(n-3).

Terms

a(0) =0a(1) =0a(2) =1a(3) =12a(4) =150a(5) =2160a(6) =36015a(7) =688128a(8) =14880348a(9) =360000000a(10) =9646149645a(11) =283787919360