a(n) = 7^n * n*(n+1).

Terms

a(0) =0a(1) =14a(2) =294a(3) =4116a(4) =48020a(5) =504210a(6) =4941258a(7) =46118408a(8) =415065672a(9) =3631824630a(10) =31072277390a(11) =261007130076