a(n) = (3^(3*n + 3)- 26*n - 27)/169.

A198080

a(n) = (3^(3*n + 3)- 26*n - 27)/169.

Terms

    a(0) =0a(1) =4a(2) =116a(3) =3144a(4) =84904a(5) =2292428a(6) =61895580a(7) =1671180688a(8) =45121878608

External references