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 A012727 #6 Nov 28 2016 19:59:02
%S A012727 1,2,12,328,13328,1160352,123701952,22207125120,4532782825728,
%T A012727 1380071532433920,459909185638812672,212375023941305272320,
%U A012727 104929881035116227072000,68350141067274779587092480
%N A012727 exp(arctanh(x)*arctan(x))=1+2/2!*x^2+12/4!*x^4+328/6!*x^6+13328/8!*x^8...
%t A012727 With[{nn=30},Take[CoefficientList[Series[Exp[ArcTanh[x]*ArcTan[x]],{x,0,nn}],x] Range[0,nn]!,{1,-1,2}]] (* _Ray Chandler_, Nov 28 2016 *)
%K A012727 nonn
%O A012727 0,2
%A A012727 Patrick Demichel (patrick.demichel(AT)hp.com)