Sequence A014486 shown in base 4.

Terms

a(0) =0a(1) =2a(2) =22a(3) =30a(4) =222a(5) =230a(6) =302a(7) =310a(8) =320a(9) =2222a(10) =2230a(11) =2302a(12) =2310a(13) =2320a(14) =3022a(15) =3030a(16) =3102a(17) =3110a(18) =3120a(19) =3202a(20) =3210a(21) =3220a(22) =3300a(23) =22222a(24) =22230a(25) =22302a(26) =22310a(27) =22320a(28) =23022a(29) =23030