a(n) = Sum_{d|n} (d-1)! * d^(n/d).

Terms

a(0) =1a(1) =3a(2) =7a(3) =29a(4) =121a(5) =747a(6) =5041a(7) =40433a(8) =362935a(9) =3629433a(10) =39916801a(11) =479006531a(12) =6227020801a(13) =87178326609