Numbers having four 9's in base 10.

Terms

a(0) =9999a(1) =19999a(2) =29999a(3) =39999a(4) =49999a(5) =59999a(6) =69999a(7) =79999a(8) =89999a(9) =90999a(10) =91999a(11) =92999a(12) =93999a(13) =94999a(14) =95999a(15) =96999a(16) =97999a(17) =98999a(18) =99099a(19) =99199a(20) =99299a(21) =99399a(22) =99499a(23) =99599a(24) =99699a(25) =99799a(26) =99899a(27) =99909a(28) =99919a(29) =99929