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 A039684 #5 Jun 28 2020 10:28:46 %S A039684 1089,10989,109989,1099989,10999989,109999989 %N A039684 Erroneous version of A001232. %K A039684 dead %O A039684 1,1