Numbers with exactly two 3's in their base 4 expansion.

Terms

a(0) =15a(1) =31a(2) =47a(3) =51a(4) =55a(5) =59a(6) =60a(7) =61a(8) =62a(9) =79a(10) =95a(11) =111a(12) =115a(13) =119a(14) =123a(15) =124a(16) =125a(17) =126a(18) =143a(19) =159a(20) =175a(21) =179a(22) =183a(23) =187a(24) =188a(25) =189a(26) =190a(27) =195a(28) =199a(29) =203