Smallest number whose sum of digits is 3n.

Terms

a(0) =0a(1) =3a(2) =6a(3) =9a(4) =39a(5) =69a(6) =99a(7) =399a(8) =699a(9) =999a(10) =3999a(11) =6999a(12) =9999a(13) =39999a(14) =69999a(15) =99999a(16) =399999a(17) =699999a(18) =999999a(19) =3999999a(20) =6999999a(21) =9999999a(22) =39999999a(23) =69999999a(24) =99999999a(25) =399999999a(26) =699999999a(27) =999999999a(28) =3999999999a(29) =6999999999