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

Terms

a(0) =1a(1) =5a(2) =36a(3) =354a(4) =4425a(5) =67171a(6) =1200304a(7) =24684612a(8) =574304985a(9) =14914341925a(10) =427675990236