a(n) = Sum_{k=1..n-1} k^n.

Terms

a(0) =0a(1) =1a(2) =9a(3) =98a(4) =1300a(5) =20515a(6) =376761a(7) =7907396a(8) =186884496a(9) =4914341925a(10) =142364319625