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 A039012 #17 Jul 14 2022 17:00:04 %S A039012 0,2,3,9,10,12,13,15,17,18,21,29,39,44,45,47,48,50,52,53,59,60,62,63, %T A039012 65,67,68,71,75,77,78,84,85,87,88,90,92,93,96,101,105,107,108,111,116, %U A039012 129,139,144,145,147,148,174,179,189,194,195,197,198,204,214,219,220 %N A039012 Numbers whose base-5 representation has the same number of 1's and 4's. %H A039012 Daniel Starodubtsev, <a href="/A039012/b039012.txt">Table of n, a(n) for n = 1..10000</a> %t A039012 Select[Range[0,250],DigitCount[#,5,1]==DigitCount[#,5,4]&] (* _Harvey P. Dale_, Jul 14 2022 *) %Y A039012 Cf. A007091. %K A039012 nonn,base,easy %O A039012 1,2 %A A039012 _Olivier Gérard_