a(n) = 3*10^n - 1.

Terms

a(0) =2a(1) =29a(2) =299a(3) =2999a(4) =29999a(5) =299999a(6) =2999999a(7) =29999999a(8) =299999999a(9) =2999999999a(10) =29999999999a(11) =299999999999