Numbers whose base-9 representation has the same nonzero number of 6's and 7's.

Terms

a(0) =61a(1) =69a(2) =142a(3) =150a(4) =223a(5) =231a(6) =304a(7) =312a(8) =385a(9) =393a(10) =466a(11) =474a(12) =493a(13) =502a(14) =511a(15) =520a(16) =529a(17) =538a(18) =549a(19) =550a(20) =551a(21) =552a(22) =553a(23) =554a(24) =557a(25) =565a(26) =573a(27) =582a(28) =591a(29) =600