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A009695
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Expansion of tan(tan(x))*cos(x) (odd powers only).
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0
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1, 1, 37, 1517, 108393, 11820345, 1828543693, 380880450277, 102776857839441, 34874008165786609, 14532999645144493557, 7296638106447614270813, 4344082656476890774001593, 3025958669024832261385239593
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OFFSET
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1,3
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LINKS
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FORMULA
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a(n) ~ (2*n-1)! * 16 / ((4+Pi^2)^(3/2) * arctan(Pi/2)^(2*n)). - Vaclav Kotesovec, Jan 23 2015
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MATHEMATICA
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Tan[ Tan[ x ] ]*Cos[ x ] (* Odd Part *)
nn = 20; Table[(CoefficientList[Series[Cos[x]*Tan[Tan[x]], {x, 0, 2*nn+1}], x] * Range[0, 2*nn+1]!)[[n]], {n, 2, 2*nn, 2}] (* Vaclav Kotesovec, Jan 23 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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EXTENSIONS
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STATUS
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approved
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