a(n) = 10*9^n-1.

Terms

a(0) =9a(1) =89a(2) =809a(3) =7289a(4) =65609a(5) =590489a(6) =5314409a(7) =47829689a(8) =430467209a(9) =3874204889a(10) =34867844009a(11) =313810596089