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

Terms

a(0) =1a(1) =6a(2) =33a(3) =328a(4) =3245a(5) =52056a(6) =828583a(7) =17328256a(8) =389416329a(9) =10105386400a(10) =285351587411