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A012725
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exp(arctanh(x)*tan(x)) = 1+2/2!*x^2+28/4!*x^4+920/6!*x^6+54416/8!*x^8...
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0
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1, 2, 28, 920, 54416, 5056288, 678865856, 124425704832, 29873423298816, 9104340085891584, 3435702339713424384, 1573394503700675106816, 859935938676055185002496, 553085284375423405752918016
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OFFSET
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0,2
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LINKS
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FORMULA
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a(n) ~ 2 * (2*n-1)! * (4*n)^(tan(1)/2) / GAMMA(tan(1)/2). - Vaclav Kotesovec, Oct 24 2013
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MATHEMATICA
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With[{nn=30}, Take[CoefficientList[Series[Exp[ArcTanh[x]Tan[x]], {x, 0, nn}], x] Range[0, nn]!, {1, -1, 2}]] (* Harvey P. Dale, Mar 25 2013 *)
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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Patrick Demichel (patrick.demichel(AT)hp.com)
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STATUS
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approved
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