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 A089540 #3 Mar 30 2012 17:29:13 %S A089540 2,2,3,5,11,7,71,61,5,11,3,97,83,23,7,2,3,263,71,20639383,11, %T A089540 281421719,3,811,401,1697,110298581317,29,33619,2,19,11,11,67411,7,3, %U A089540 126397507816417,14029308060317546154181,13,9649,53,2044687972231331951 %N A089540 Lesser prime factor of semiprimes in A089539. %Y A089540 Cf. A085747, A089538, A089539, A089541. %K A089540 nonn %O A089540 1,1 %A A089540 _Ray Chandler_, Nov 09 2003