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%I #10 Nov 28 2015 13:12:50
%S 0,2,16,152,-5504,-865888,-49313024,10192998272,4634262163456,
%T 729893872005632,-280859292338008064,-286057930617679095808,
%U -94104910901654903619584,51677977224364973979901952
%N arcsinh(tan(x)*tan(x))=2/2!*x^2+16/4!*x^4+152/6!*x^6-5504/8!*x^8...
%H Vaclav Kotesovec, <a href="/A012391/b012391.txt">Table of n, a(n) for n = 0..220</a>
%t With[{nn=30},Take[CoefficientList[Series[ArcSinh[Tan[x]^2],{x,0,nn}],x] Range[0,nn]!,{1,-1,2}]] (* _Harvey P. Dale_, Dec 14 2014 *)
%K sign
%O 0,2
%A Patrick Demichel (patrick.demichel(AT)hp.com)
%E Prepended a(0)=0 by _Vaclav Kotesovec_, Nov 28 2015