Smallest number whose sum of digits is 2n.

Terms

a(0) =0a(1) =2a(2) =4a(3) =6a(4) =8a(5) =19a(6) =39a(7) =59a(8) =79a(9) =99a(10) =299a(11) =499a(12) =699a(13) =899a(14) =1999a(15) =3999a(16) =5999a(17) =7999a(18) =9999a(19) =29999a(20) =49999a(21) =69999a(22) =89999a(23) =199999a(24) =399999a(25) =599999a(26) =799999a(27) =999999a(28) =2999999a(29) =4999999