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

Terms

a(0) =0a(1) =1a(2) =6a(3) =39a(4) =340a(5) =3905a(6) =55986a(7) =960799a(8) =19173960a(9) =435848049a(10) =11111111110a(11) =313842837671