Numbers whose base-7 representation has the same nonzero number of 0's and 6's.

Terms

a(0) =42a(1) =55a(2) =91a(3) =104a(4) =140a(5) =153a(6) =189a(7) =202a(8) =238a(9) =251a(10) =287a(11) =295a(12) =296a(13) =297a(14) =298a(15) =299a(16) =301a(17) =308a(18) =315a(19) =322a(20) =329a(21) =356a(22) =363a(23) =370a(24) =377a(25) =384a(26) =386a(27) =387a(28) =388a(29) =389