a(n) = Sum_{d|n} C(n,d)^(n/d).

Terms

a(0) =1a(1) =5a(2) =28a(3) =293a(4) =3126a(5) =50432a(6) =823544a(7) =17396773a(8) =388013194a(9) =10184591630a(10) =285311670612