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

Terms

a(0) =1a(1) =6a(2) =30a(3) =324a(4) =3130a(5) =53070a(6) =823550a(7) =17829896a(8) =387951939a(9) =10312525610a(10) =285311670622