a(0) = 0; for n>0, a(n) = 9*n!.

Terms

a(0) =0a(1) =9a(2) =18a(3) =54a(4) =216a(5) =1080a(6) =6480a(7) =45360a(8) =362880a(9) =3265920a(10) =32659200a(11) =359251200a(12) =4311014400a(13) =56043187200a(14) =784604620800