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E.g.f.: exp(arctan(arctan(x))) = 1+x+1/2!*x^2-3/3!*x^3-15/4!*x^4+49/5!*x^5...
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%I #11 Aug 15 2014 03:18:10

%S 1,1,1,-3,-15,49,609,-1859,-48031,119617,6247681,-10283171,

%T -1214813487,678311217,330587407201,246695568861,-120086685689663,

%U -270153706006015,56186566871496961,221300400903581245

%N E.g.f.: exp(arctan(arctan(x))) = 1+x+1/2!*x^2-3/3!*x^3-15/4!*x^4+49/5!*x^5...

%H Vincenzo Librandi, <a href="/A012203/b012203.txt">Table of n, a(n) for n = 0..200</a>

%t With[{nn=20},CoefficientList[Series[Exp[ArcTan[ArcTan[x]]],{x,0,nn}],x] Range[0,nn]!] (* _Harvey P. Dale_, Aug 14 2014 *)

%K sign

%O 0,4

%A Patrick Demichel (patrick.demichel(AT)hp.com)

%E Definition edited and clarified by _Harvey P. Dale_, Aug 14 2014