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A012618
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arctanh(arcsinh(x)*tan(x))=2/2!*x^2+4/4!*x^4+350/6!*x^6+7208/8!*x^8...
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0
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0, 2, 4, 350, 7208, 1520218, 106485740, 38051376246, 6123846322896, 3217389043510578, 964215477538459732, 692917532440212444686, 338776184246581290006520, 318786053587029917056642186
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OFFSET
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0,2
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LINKS
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Table of n, a(n) for n=0..13.
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FORMULA
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a(n) ~ (2*n-1)! / r^(2*n), where r = 0.89357177742189289... is the root of the equation r+sqrt(r^2+1) = exp(1/tan(r)). - Vaclav Kotesovec, Oct 31 2013
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MATHEMATICA
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Table[n!*SeriesCoefficient[ArcTanh[ArcSinh[x]*Tan[x]], {x, 0, n}], {n, 0, 40, 2}] (* Vaclav Kotesovec, Oct 31 2013 *)
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CROSSREFS
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Sequence in context: A009705 A012372 A012613 * A012557 A012562 A263959
Adjacent sequences: A012615 A012616 A012617 * A012619 A012620 A012621
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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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Prepended missing a(0)=0 from Vaclav Kotesovec, Oct 31 2013
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STATUS
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approved
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