a(n) = 3^(2*n) + 7.

Terms

a(0) =8a(1) =16a(2) =88a(3) =736a(4) =6568a(5) =59056a(6) =531448a(7) =4782976a(8) =43046728a(9) =387420496a(10) =3486784408a(11) =31381059616a(12) =282429536488