Numbers whose set of base 10 digits is {0,9}.

Terms

a(0) =0a(1) =9a(2) =90a(3) =99a(4) =900a(5) =909a(6) =990a(7) =999a(8) =9000a(9) =9009a(10) =9090a(11) =9099a(12) =9900a(13) =9909a(14) =9990a(15) =9999a(16) =90000a(17) =90009a(18) =90090a(19) =90099a(20) =90900a(21) =90909a(22) =90990a(23) =90999a(24) =99000a(25) =99009a(26) =99090a(27) =99099a(28) =99900a(29) =99909