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 A039291 #15 Jun 28 2021 04:34:52 %S A039291 14,22,39,47,54,59,69,70,71,73,89,97,102,107,110,111,113,117,139,147, %T A039291 164,172,179,184,194,195,196,198,214,222,227,232,235,236,238,242,254, %U A039291 259,269,270,271,273,279,284,294,295,296,298,324,329,334,344,345,346 %N A039291 Numbers whose base-5 representation has the same nonzero number of 2's and 4's. %t A039291 Select[Range[400],DigitCount[#,5,2]==DigitCount[#,5,4]>0&] (* _Harvey P. Dale_, Apr 26 2011 *) %Y A039291 Cf. A007091. %K A039291 nonn,base,easy %O A039291 1,1 %A A039291 _Olivier Gérard_