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%I #10 Jul 23 2014 03:23:47
%S 1,-1,-11,-301,-14839,-1109881,-110852675,-12696026981,-1044878845295,
%T 344502726652559,397767671438223365,311149018395487011299,
%U 242840543036206414510489,203578596149994366707196439,187397387863859771967571124941,190632732651754400283645304176299
%N sech(tan(arctanh(x)))=1-1/2!*x^2-11/4!*x^4-301/6!*x^6-14839/8!*x^8...
%H Vincenzo Librandi, <a href="/A012184/b012184.txt">Table of n, a(n) for n = 0..40</a>
%t With[{nn=40},Take[CoefficientList[Series[Sech[Tan[ArcTanh[x]]],{x,0,nn}],x] Range[0,nn]!,{1,-1,2}]] (* _Harvey P. Dale_, Jul 22 2014 *)
%K sign
%O 0,3
%A Patrick Demichel (patrick.demichel(AT)hp.com)
%E More terms from _Harvey P. Dale_, Jul 22 2014