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 A023709 #13 Sep 13 2023 07:27:45 %S A023709 0,2,3,8,10,11,12,14,15,32,34,35,40,42,43,44,46,47,48,50,51,56,58,59, %T A023709 60,62,63,128,130,131,136,138,139,140,142,143,160,162,163,168,170,171, %U A023709 172,174,175,176,178,179,184,186,187,188 %N A023709 Numbers with no 1's in their base 4 expansion. %H A023709 Seiichi Manyama, <a href="/A023709/b023709.txt">Table of n, a(n) for n = 1..10000</a> %t A023709 Select[ Range[ 0, 200 ], (Count[ IntegerDigits[ #, 4 ], 1 ]==0)& ] %K A023709 nonn,base,easy %O A023709 1,2 %A A023709 _Olivier Gérard_