a(n) = 3^n + 6^n + 8^n.

Terms

a(0) =3a(1) =17a(2) =109a(3) =755a(4) =5473a(5) =40787a(6) =309529a(7) =2379275a(8) =18463393a(9) =144315107a(10) =1134267049a(11) =8952908795a(12) =70896790513a(13) =562818102227