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 A023401 #13 Jan 27 2022 22:45:08 %S A023401 4,4,1,4,1,4,1,4,4,1,1,4,4,4,4,1,4,4,1,4,1,1,1,4,1,1,1,4,4,4,1,1,4,1, %T A023401 1,1,1,1,1,4,4,4,1,1,1,4,4,4,4,4,4,1,4,4,4,4,1,1,4,1,4,4,1,4,1,4,4,4, %U A023401 1,1,1,4,4,4,4,4,1,1,4,4,1,4,4,1,1,4,1,1,1,1,4,4,4,1,4,4,4,1,1,1,4,1,4,4,4,1,1,4 %N A023401 If any even power of 2 ends with k 1's and 4's, they must be the first k terms of this sequence in reverse order. %H A023401 Ray Chandler, <a href="/A023401/b023401.txt">Table of n, a(n) for n = 1..10000</a> %K A023401 nonn,base %O A023401 1,1 %A A023401 _David W. Wilson_