Numbers with exactly two distinct base-4 digits.

Terms

a(0) =4a(1) =6a(2) =7a(3) =8a(4) =9a(5) =11a(6) =12a(7) =13a(8) =14a(9) =16a(10) =17a(11) =20a(12) =22a(13) =23a(14) =25a(15) =26a(16) =29a(17) =31a(18) =32a(19) =34a(20) =37a(21) =38a(22) =40a(23) =41a(24) =43a(25) =46a(26) =47a(27) =48a(28) =51a(29) =53