8^n-5^n+1^n.

Terms

a(0) =1a(1) =4a(2) =40a(3) =388a(4) =3472a(5) =29644a(6) =246520a(7) =2019028a(8) =16386592a(9) =132264604a(10) =1063976200a(11) =8541106468a(12) =68475336112a(13) =548535110764