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

Terms

a(0) =0a(1) =0a(2) =1a(3) =9a(4) =96a(5) =1250a(6) =19440a(7) =352947a(8) =7340032a(9) =172186884a(10) =4500000000a(11) =129687123005