a(n) = 2^n + 9^n.

Terms

a(0) =2a(1) =11a(2) =85a(3) =737a(4) =6577a(5) =59081a(6) =531505a(7) =4783097a(8) =43046977a(9) =387421001a(10) =3486785425a(11) =31381061657a(12) =282429540577