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 A039015 #14 Jun 20 2021 14:57:53 %S A039015 0,1,2,5,6,7,10,11,12,19,23,25,26,27,30,31,32,35,36,37,44,48,50,51,52, %T A039015 55,56,57,60,61,62,69,73,79,84,89,95,96,97,103,108,113,115,116,117, %U A039015 125,126,127,130,131,132,135,136,137,144,148,150,151,152,155,156,157 %N A039015 Numbers whose base-5 representation has the same number of 3's and 4's. %H A039015 Daniel Starodubtsev, <a href="/A039015/b039015.txt">Table of n, a(n) for n = 1..10000</a> %t A039015 Select[Range[0,200],DigitCount[#,5,3]==DigitCount[#,5,4]&] (* _Harvey P. Dale_, Oct 08 2017 *) %Y A039015 Cf. A007091. %K A039015 nonn,base,easy %O A039015 1,3 %A A039015 _Olivier Gérard_