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A012165
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tanh(tan(arcsinh(x)))=x-1/3!*x^3+1/5!*x^5-57/7!*x^7+4513/9!*x^9...
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1
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1, -1, 1, -57, 4513, -362737, 43685409, -7472568937, 1694762362561, -492370173816033, 178467092014537921, -78960125273223620761, 41880334808869380979041, -26232480244560931030777297
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history;
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internal format)
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OFFSET
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0,4
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LINKS
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FORMULA
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a(n) ~ (-1)^n * c * (2*n)! / sqrt(n), where c = 0.2423459676113260058762976897... . - Vaclav Kotesovec, Feb 03 2015
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MATHEMATICA
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With[{nn=30}, Take[CoefficientList[Series[Tanh[Tan[ArcSinh[x]]], {x, 0, nn}], x] Range[0, nn-1]!, {2, -1, 2}]] (* Harvey P. Dale, Jun 19 2013 *)
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CROSSREFS
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KEYWORD
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sign
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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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