a(n) = floor(10^(n+1)/81).

Terms

a(0) =0a(1) =1a(2) =12a(3) =123a(4) =1234a(5) =12345a(6) =123456a(7) =1234567a(8) =12345679a(9) =123456790a(10) =1234567901a(11) =12345679012a(12) =123456790123