a(n) = 11*10^n - 1.

Terms

a(0) =10a(1) =109a(2) =1099a(3) =10999a(4) =109999a(5) =1099999a(6) =10999999a(7) =109999999a(8) =1099999999a(9) =10999999999a(10) =109999999999