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 A023399 #13 Jan 27 2022 22:44:38 %S A023399 2,7,2,2,2,2,7,2,7,2,7,7,7,7,2,2,7,2,7,2,7,7,2,7,7,2,7,2,7,7,2,2,2,2, %T A023399 7,2,7,2,7,2,2,2,7,7,7,7,2,2,7,7,7,2,7,2,2,7,7,7,7,2,7,7,2,7,7,2,7,7, %U A023399 7,7,7,2,2,7,2,7,7,7,7,7,2,2,7,7,2,2,7,7,2,7,2,7,2,7,2,7,2,7,2,7,2,2,7,2,7,7,2,7 %N A023399 If any power of 2 ends with k 2's and 7's, they must be the first k terms of this sequence in reverse order. %H A023399 Ray Chandler, <a href="/A023399/b023399.txt">Table of n, a(n) for n = 1..10000</a> %K A023399 nonn,base %O A023399 1,1 %A A023399 _David W. Wilson_