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 A089543 #3 Mar 30 2012 17:29:13 %S A089543 2,2,3,7,53,29,353,1549,8353,7,15889,1691419,347,67,1097,274177,43, %T A089543 18882774223,67,5197,1801088543,556114086547,44773,3062989,5641, %U A089543 92553847628747,18349361,607,51131,13217,42806180589950051 %N A089543 Lesser prime factor of semiprimes in A089542. %Y A089543 Cf. A085753, A089542, A089544. %K A089543 nonn %O A089543 1,1 %A A089543 _Ray Chandler_, Nov 09 2003