a(n) = 2^n + 3^n + 9^n.

Terms

a(0) =3a(1) =14a(2) =94a(3) =764a(4) =6658a(5) =59324a(6) =532234a(7) =4785284a(8) =43053538a(9) =387440684a(10) =3486844474a(11) =31381238804a(12) =282430072018