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

Terms

a(0) =1a(1) =6a(2) =33a(3) =472a(4) =3245a(5) =157896a(6) =828583a(7) =132078976a(8) =1578211209a(9) =307174074400a(10) =285351587411