a(n) = n! - 2^n.

Terms

a(0) =0a(1) =-1a(2) =-2a(3) =-2a(4) =8a(5) =88a(6) =656a(7) =4912a(8) =40064a(9) =362368a(10) =3627776a(11) =39914752a(12) =478997504a(13) =6227012608a(14) =87178274816