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

Terms

a(0) =0a(1) =1a(2) =10a(3) =91a(4) =820a(5) =7381a(6) =66430a(7) =597871a(8) =5380840a(9) =48427561a(10) =435848050a(11) =3922632451a(12) =35303692060a(13) =317733228541