a(n) = 9^n - n.

Terms

a(0) =1a(1) =8a(2) =79a(3) =726a(4) =6557a(5) =59044a(6) =531435a(7) =4782962a(8) =43046713a(9) =387420480a(10) =3486784391a(11) =31381059598a(12) =282429536469