a(n) = 3*n*n!.

Terms

a(0) =0a(1) =3a(2) =12a(3) =54a(4) =288a(5) =1800a(6) =12960a(7) =105840a(8) =967680a(9) =9797760a(10) =108864000a(11) =1317254400a(12) =17244057600a(13) =242853811200