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 A143681 #9 Mar 01 2021 06:39:31 %S A143681 1,1,1,1,9,1,1,17,17,1,1,25,97,25,1,1,33,241,241,33,1,1,41,449,1161, %T A143681 449,41,1,1,49,721,3297,3297,721,49,1,1,57,1057,7161,14721,7161,1057, %U A143681 57,1,1,65,1457,13265 %N A143681 Duplicate of A081582. %K A143681 dead %O A143681 0,5