a(n) = Sum_{k=0..n} n^k.

Terms

a(0) =1a(1) =2a(2) =7a(3) =40a(4) =341a(5) =3906a(6) =55987a(7) =960800a(8) =19173961a(9) =435848050a(10) =11111111111a(11) =313842837672