a(n) = n!*tribonacci(n+2).

Terms

a(0) =1a(1) =1a(2) =4a(3) =24a(4) =168a(5) =1560a(6) =17280a(7) =221760a(8) =3265920a(9) =54069120a(10) =994291200a(11) =20118067200a(12) =444034483200