a(n) = 10^n - 9.

Terms

a(0) =1a(1) =91a(2) =991a(3) =9991a(4) =99991a(5) =999991a(6) =9999991a(7) =99999991a(8) =999999991a(9) =9999999991a(10) =99999999991a(11) =999999999991