a(n) = 2^n + 8^n + 9^n.

Terms

a(0) =3a(1) =19a(2) =149a(3) =1249a(4) =10673a(5) =91849a(6) =793649a(7) =6880249a(8) =59824193a(9) =521638729a(10) =4560527249a(11) =39970996249a(12) =351149017313