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 A039411 #11 Jun 30 2021 03:58:05 %S A039411 24,42,124,142,204,214,234,240,241,243,245,246,247,248,249,254,264, %T A039411 274,284,294,324,342,402,412,420,421,423,425,426,427,428,429,432,452, %U A039411 462,472,482,492,524,542,624,642,724,742,824,842,924,942,1024,1042 %N A039411 Numbers whose base-10 representation has the same nonzero number of 2's and 4's. %K A039411 nonn,base,easy %O A039411 1,1 %A A039411 _Olivier Gérard_