Numbers whose base-12 representation has the same nonzero number of 1's and 9's.

Terms

a(0) =21a(1) =109a(2) =153a(3) =177a(4) =189a(5) =201a(6) =213a(7) =225a(8) =237a(9) =249a(10) =252a(11) =254a(12) =255a(13) =256a(14) =257a(15) =258a(16) =259a(17) =260a(18) =262a(19) =263a(20) =273a(21) =285a(22) =309a(23) =397a(24) =453a(25) =541a(26) =597a(27) =685a(28) =741a(29) =829