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 A043333 #21 Apr 24 2021 01:59:56
%S A043333 4,8,12,17,18,19,20,24,28,33,34,35,36,40,44,49,50,51,52,56,60,69,70,
%T A043333 71,73,74,75,77,78,79,81,82,83,84,88,92,97,98,99,100,104,108,113,114,
%U A043333 115,116,120,124,133,134,135,137,138,139,141,142
%N A043333 Numbers having one 0 in base 4.
%F A043333 A023706 \ {0}. - _R. J. Mathar_, Oct 20 2008
%t A043333 Select[Range[150],DigitCount[#,4,0]==1&] (* _Harvey P. Dale_, Jul 23 2011 *)
%Y A043333 Cf. A007090.
%K A043333 nonn,base
%O A043333 1,1
%A A043333 _Clark Kimberling_