Numbers whose base-7 representation has the same nonzero number of 0's and 3's.

Terms

a(0) =21a(1) =52a(2) =70a(3) =101a(4) =119a(5) =148a(6) =149a(7) =151a(8) =152a(9) =153a(10) =154a(11) =161a(12) =175a(13) =182a(14) =189a(15) =199a(16) =217a(17) =248a(18) =266a(19) =297a(20) =315a(21) =353a(22) =360a(23) =365a(24) =366a(25) =368a(26) =369a(27) =370a(28) =374a(29) =381