This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A111066 #21 Dec 21 2021 11:53:59
%S A111066 12,21,112,121,122,211,212,221,1112,1121,1122,1211,1212,1221,1222,
%T A111066 2111,2112,2121,2122,2211,2212,2221,11112,11121,11122,11211,11212,
%U A111066 11221,11222,12111,12112,12121,12122,12211,12212,12221,12222,21111,21112,21121,21122,21211
%N A111066 Numbers with digits 1 and 2 and at least one of each.
%H A111066 Harvey P. Dale, <a href="/A111066/b111066.txt">Table of n, a(n) for n = 1..1000</a>
%t A111066 FromDigits /@ Select[ IntegerDigits[ Range[210], 3], Union[ # ] == {1, 2} &] (* _Robert G. Wilson v_, Oct 09 2005 *)
%t A111066 Union[FromDigits/@Select[Flatten[Table[Tuples[{1,2},n],{n,2,5}],1], Union[#] == {1,2}&]] (* _Harvey P. Dale_, Sep 05 2013 *)
%o A111066 (Python)
%o A111066 from itertools import count, islice
%o A111066 def agen():
%o A111066 for i in count(1):
%o A111066 s = bin(i+1)[3:].replace('1', '2').replace('0', '1')
%o A111066 if 0 < s.count('1') < len(s):
%o A111066 yield int(s)
%o A111066 print(list(islice(agen(), 42))) # _Michael S. Branicky_, Dec 21 2021
%Y A111066 Equals A007931 minus A000042 and A002276. Supersequence of A214218.
%Y A111066 Cf. A043494, A037415, A062289, A000225.
%K A111066 easy,nonn,base
%O A111066 1,1
%A A111066 _Alexandre Wajnberg_ & Youri Mora, Oct 08 2005
%E A111066 More terms from _Robert G. Wilson v_, Oct 09 2005
%E A111066 Crossrefs from _Charles R Greathouse IV_, Aug 03 2010