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 A012251 #11 Dec 21 2013 22:36:43
%S A012251 1,1,1,-2,-11,24,349,-720,-22455,40320,2465241,-3628800,-416217603,
%T A012251 479001600,100729124469,-87178291200,-33198564667887,20922789888000,
%U A012251 14328891118054449,-6402373705728000,-7852649782447649403
%N A012251 exp(arcsinh(arctan(x)))=1+x+1/2!*x^2-2/3!*x^3-11/4!*x^4+24/5!*x^5...
%F A012251 E.g.f.: Q(0)-1, where Q(k) = 2 + arctan(x)/(1 - arctan(x)/Q(k+1) ); (continued fraction). - _Sergei N. Gladkovskii_, Dec 19 2013
%t A012251 With[{nn=30},CoefficientList[Series[Exp[ArcSinh[ArcTan[x]]],{x,0,nn}],x] Range[0,nn]!] (* _Harvey P. Dale_, Oct 26 2011 *)
%Y A012251 Bisections are (-1)^n*A010050 and (-1)^n*A012138.
%K A012251 sign
%O A012251 0,4
%A A012251 Patrick Demichel (patrick.demichel(AT)hp.com)