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

Terms

a(0) =63a(1) =127a(2) =191a(3) =207a(4) =223a(5) =239a(6) =243a(7) =247a(8) =251a(9) =252a(10) =253a(11) =254a(12) =319a(13) =383a(14) =447a(15) =463a(16) =479a(17) =495a(18) =499a(19) =503a(20) =507a(21) =508a(22) =509a(23) =510a(24) =575a(25) =639a(26) =703a(27) =719a(28) =735a(29) =751