Numbers whose base-11 representation has the same nonzero number of 1's and 2's.

Terms

a(0) =13a(1) =23a(2) =123a(3) =143a(4) =146a(5) =147a(6) =148a(7) =149a(8) =150a(9) =151a(10) =152a(11) =153a(12) =156a(13) =167a(14) =178a(15) =189a(16) =200a(17) =211a(18) =222a(19) =233a(20) =243a(21) =253a(22) =256a(23) =257a(24) =258a(25) =259a(26) =260a(27) =261a(28) =262a(29) =263