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 A173716 #11 Jul 11 2015 16:15:07 %S A173716 4,46,469,10469,101469,10141569,101421569,1014221569,101421522569, %T A173716 1014215225269,101421522526339,1014215225263349,101421522526334359, %U A173716 10142152252633435389,101421522526334353839,1014215225263346353839 %N A173716 Smallest number that contains the first n semiprimes as substrings. %C A173716 Semiprime analog of A054261. %D A173716 Jonathan Vos Post, Posting to the Sequence Fans Mailing List, May 24 2010 %Y A173716 Cf. A000040, A001358, A054260, A035239, A178057, A144565, A169798. %K A173716 nonn,base,more %O A173716 1,1 %A A173716 _N. J. A. Sloane_, Nov 25 2010 %E A173716 More terms from _Sean A. Irvine_, Dec 02 2010