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A012717
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arctanh(arctanh(x)*exp(x))=x+2/2!*x^2+7/3!*x^3+36/4!*x^4+293/5!*x^5...
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0
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0, 1, 2, 7, 36, 293, 2710, 31099, 408072, 6199465, 105183658, 1990233551, 41337728300, 937722749325, 23029648705726, 609300643351555, 17268619403747600, 522102791124578001, 16771008730706230098
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OFFSET
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0,3
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LINKS
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FORMULA
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a(n) ~ (n-1)!/(2*(tanh(r/2))^n), where r = 1.17812663495672544... is the root of the equation r*exp((exp(r)-1)/(exp(r)+1)) = 2. - Vaclav Kotesovec, Oct 24 2013
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MATHEMATICA
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CoefficientList[Series[ArcTanh[ArcTanh[x]*Exp[x]], {x, 0, 20}], x]* Range[0, 20]! (* Vaclav Kotesovec, Oct 24 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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EXTENSIONS
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STATUS
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approved
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