a(n) = 9^n-n^5.

Terms

a(0) =1a(1) =8a(2) =49a(3) =486a(4) =5537a(5) =55924a(6) =523665a(7) =4766162a(8) =43013953a(9) =387361440a(10) =3486684401a(11) =31380898558a(12) =282429287649