a(n+1) = smallest number not containing any digits of a(n), working in base 4.

Terms

a(0) =0a(1) =1a(2) =2a(3) =3a(4) =4a(5) =10a(6) =12a(7) =21a(8) =32a(9) =53a(10) =128a(11) =213a(12) =512a(13) =853a(14) =2048a(15) =3413a(16) =8192a(17) =13653a(18) =32768a(19) =54613a(20) =131072a(21) =218453a(22) =524288a(23) =873813a(24) =2097152a(25) =3495253a(26) =8388608a(27) =13981013a(28) =33554432a(29) =55924053