9^n - 5^n + 1.

Terms

a(0) =1a(1) =5a(2) =57a(3) =605a(4) =5937a(5) =55925a(6) =515817a(7) =4704845a(8) =42656097a(9) =385467365a(10) =3477018777a(11) =31332231485a(12) =282185395857