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 A043498 #29 Apr 24 2021 21:08:28
%S A043498 22,122,202,212,220,221,223,224,225,226,227,228,229,232,242,252,262,
%T A043498 272,282,292,322,422,522,622,722,822,922,1022,1122,1202,1212,1220,
%U A043498 1221,1223,1224,1225,1226,1227,1228,1229,1232,1242,1252
%N A043498 Numbers having two 2's in base 10.
%H A043498 Daniel Starodubtsev, <a href="/A043498/b043498.txt">Table of n, a(n) for n = 1..10000</a>
%p A043498 q:= n-> numboccur(2, convert(n, base, 10))=2:
%p A043498 select(q, [$2..2222])[]; # _Alois P. Heinz_, Mar 15 2020
%t A043498 Select[Range[5000], DigitCount[#, 10, 2] == 2 &] (* _Vincenzo Librandi_, Nov 20 2015 *)
%o A043498 (PARI) c(k, d, b) = {my(c=0, f); while (k>b-1, f=k-b*(k\b); if (f==d, c++); k\=b); if (k==d, c++); return(c)}
%o A043498 for(n=0, 2000, if(c(n, 2, 10)==2, print1(n, ", "))) \\ _Altug Alkan_, Nov 20 2015
%Y A043498 Subsequence of A011532.
%K A043498 nonn,base
%O A043498 1,1
%A A043498 _Clark Kimberling_