a(n) = 9^n + 8^n - 1.

Terms

a(0) =1a(1) =16a(2) =144a(3) =1240a(4) =10656a(5) =91816a(6) =793584a(7) =6880120a(8) =59823936a(9) =521638216a(10) =4560526224a(11) =39970994200a(12) =351149013216