Numbers whose base-3 representation has the same nonzero number of 0's and 1's.

Terms

a(0) =3a(1) =11a(2) =15a(3) =19a(4) =21a(5) =28a(6) =30a(7) =35a(8) =36a(9) =47a(10) =51a(11) =59a(12) =61a(13) =65a(14) =69a(15) =73a(16) =75a(17) =86a(18) =88a(19) =92a(20) =96a(21) =100a(22) =102a(23) =107a(24) =110a(25) =114a(26) =126a(27) =136a(28) =138a(29) =143