a(n) = (5*9^n - 1)/2.

Terms

a(0) =2a(1) =22a(2) =202a(3) =1822a(4) =16402a(5) =147622a(6) =1328602a(7) =11957422a(8) =107616802a(9) =968551222a(10) =8716961002a(11) =78452649022a(12) =706073841202