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A013052
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arctanh(sinh(x)+tan(x))=2*x+19/3!*x^3+1025/5!*x^5+138129/7!*x^7...
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0
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2, 19, 1025, 138129, 34734545, 14037224089, 8320152726665, 6799527662204049, 7327672308214372385, 10068470883926665540009, 17180000319605942481431705, 35640287243130630709541583969
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OFFSET
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0,1
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LINKS
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FORMULA
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a(n) ~ (2*n)! / r^(2*n+1), where r = 0.47191303538345047716706116017105574144998... is the root of the equation sinh(r)+tan(r) = 1. - Vaclav Kotesovec, Feb 05 2015
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MATHEMATICA
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nn = 20; Table[(CoefficientList[Series[ArcTanh[Sinh[x] + Tan[x]], {x, 0, 2*nn+1}], x] * Range[0, 2*nn+1]!)[[n]], {n, 2, 2*nn, 2}] (* Vaclav Kotesovec, Feb 05 2015 *)
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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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