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 A015058 #4 Mar 30 2012 17:20:37
%S A015058 1,1,17,4305,17685969,1158222948817,1214707441621563857,
%T A015058 20378476519005090654009809,5470368244500158631765129973873105,
%U A015058 23494985488623606981701685225398976313178577
%N A015058 q-Catalan numbers (binomial version) for q=-4.
%F A015058 {1 / (n+1)_q} {2 n choose n}_q.
%K A015058 nonn,easy
%O A015058 0,3
%A A015058 _Olivier Gérard_