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 A048826 #13 Dec 19 2015 14:15:33 %S A048826 2,3,5,19,1093,12721,4062241 %N A048826 a(n) = least k such that A048825(k) = n. %Y A048826 Cf. A048827. %K A048826 nonn,more %O A048826 0,1 %A A048826 _Christian G. Bower_, May 15 1999 %E A048826 a(6) from _Max Alekseyev_, Jun 13 2011