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A012351
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sech(arcsin(x)*arcsin(x))=1-12/4!*x^4-240/6!*x^6-1008/8!*x^8...
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0
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1, 0, -12, -240, -1008, 378240, 32163648, -363487488, -690754821888, -145507353366528, -11585562008128512, 3150884675987558400, 573373842109571665920, -1149448245885758287872000
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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) ~ -sqrt(Pi) * sinh(Pi^2/4) * (2*n)! / (n^(3/2) * (1 + cosh(Pi^2/2))). - Vaclav Kotesovec, Feb 08 2015
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MATHEMATICA
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nn = 20; Table[(CoefficientList[Series[Sech[ArcSin[x]^2], {x, 0, 2*nn}], x] * Range[0, 2*nn]!)[[n]], {n, 1, 2*nn+1, 2}] (* Vaclav Kotesovec, Feb 08 2015 *)
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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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