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 A089561 #3 Mar 30 2012 17:29:13 %S A089561 1,31,431,5431,75431,1475431,91475431,691475431,57691475431, %T A089561 1357691475431,181357691475431,17181357691475431,1617181357691475431, %U A089561 121617181357691475431,20121617181357691475431 %N A089561 Concatenations arising in A089560. %Y A089561 Cf. A089710, A089711, A089560-A089573. %K A089561 base,nonn %O A089561 1,2 %A A089561 _Ray Chandler_, Nov 22 2003