a(n) = floor( exp(1/16)*n! ).

Terms

a(0) =1a(1) =2a(2) =6a(3) =25a(4) =127a(5) =766a(6) =5365a(7) =42920a(8) =386283a(9) =3862837a(10) =42491212a(11) =509894549a(12) =6628629137a(13) =92800807920