a(n) = 9^n-2^n+1^n.

Terms

a(0) =1a(1) =8a(2) =78a(3) =722a(4) =6546a(5) =59018a(6) =531378a(7) =4782842a(8) =43046466a(9) =387419978a(10) =3486783378a(11) =31381057562a(12) =282429532386