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 A012450 #6 Feb 24 2012 12:50:50 %S A012450 2,0,40,-2688,210208,-13038080,2241915520,-589026013184, %T A012450 146361182839296,-42690102749216768,18963982821764573184, %U A012450 -10109322351828827471872,5702647873782168851521536 %N A012450 arcsinh(arctan(x)*tan(x))=2/2!*x^2+40/6!*x^6-2688/8!*x^8+210208/10!*x^10... %F A012450 a(n) = (2n)! [ x^(2n) ] arcsinh(arctan(x)*tan(x)). %K A012450 sign %O A012450 1,1 %A A012450 Patrick Demichel (patrick.demichel(AT)hp.com)