Numbers whose base-10 representation has the same nonzero number of 7's and 9's.

Terms

a(0) =79a(1) =97a(2) =179a(3) =197a(4) =279a(5) =297a(6) =379a(7) =397a(8) =479a(9) =497a(10) =579a(11) =597a(12) =679a(13) =697a(14) =709a(15) =719a(16) =729a(17) =739a(18) =749a(19) =759a(20) =769a(21) =789a(22) =790a(23) =791a(24) =792a(25) =793a(26) =794a(27) =795a(28) =796a(29) =798