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 A023713 #12 Sep 13 2023 07:27:10 %S A023713 0,1,3,4,5,7,12,13,15,16,17,19,20,21,23,28,29,31,48,49,51,52,53,55,60, %T A023713 61,63,64,65,67,68,69,71,76,77,79,80,81,83,84,85,87,92,93,95,112,113, %U A023713 115,116,117,119,124,125,127,192,193,195,196 %N A023713 Numbers with no 2's in their base 4 expansion. %H A023713 Seiichi Manyama, <a href="/A023713/b023713.txt">Table of n, a(n) for n = 1..10000</a> %t A023713 Select[ Range[ 0, 200 ], (Count[ IntegerDigits[ #, 4 ], 2 ]==0)& ] %K A023713 nonn,base,easy %O A023713 1,3 %A A023713 _Olivier Gérard_