a(n) = 10*6^n - 1.

Terms

a(0) =9a(1) =59a(2) =359a(3) =2159a(4) =12959a(5) =77759a(6) =466559a(7) =2799359a(8) =16796159a(9) =100776959a(10) =604661759a(11) =3627970559a(12) =21767823359a(13) =130606940159a(14) =783641640959