a(n) = n^2*7^n.

Terms

a(0) =0a(1) =7a(2) =196a(3) =3087a(4) =38416a(5) =420175a(6) =4235364a(7) =40353607a(8) =368947264a(9) =3268642167a(10) =28247524900a(11) =239256535903