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 A260321 #6 Jul 23 2015 12:30:11 %S A260321 -1,0,2,12,312,9600,410800,23879520,1749363840,159591720960 %N A260321 Erroneous version of A094047. %H A260321 H. M. Taylor, <a href="/A000179/a000179.pdf">A problem on arrangements</a>, Mess. Math., 32 (1902), 60ff. [Annotated scanned copy] %K A260321 dead %O A260321 1,3