a(n) = 1^n + 6^n + 8^n.

Terms

a(0) =3a(1) =15a(2) =101a(3) =729a(4) =5393a(5) =40545a(6) =308801a(7) =2377089a(8) =18456833a(9) =144295425a(10) =1134208001a(11) =8952731649a(12) =70896259073a(13) =562816507905