(n+1)!*(n+3)-3.

Terms

a(0) =5a(1) =27a(2) =141a(3) =837a(4) =5757a(5) =45357a(6) =403197a(7) =3991677a(8) =43545597a(9) =518918397a(10) =6706022397a(11) =93405311997