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 A250296 #13 Jun 08 2015 02:25:33 %S A250296 3,4,7,11,17,27,31,124,157,247 %N A250296 Number n such that A057137(n) is a semiprime. %C A250296 First unknown: 397. %e A250296 a(4) = 11 so A057137(11) = 12345678901 = 857 * 14405693 is a semiprime. %Y A250296 Cf. A120819, A057137, A046461. %K A250296 nonn,base %O A250296 1,1 %A A250296 _Eric Chen_, Dec 25 2014