a(n) = n! + 1.

Terms

a(0) =2a(1) =2a(2) =3a(3) =7a(4) =25a(5) =121a(6) =721a(7) =5041a(8) =40321a(9) =362881a(10) =3628801a(11) =39916801a(12) =479001601a(13) =6227020801a(14) =87178291201