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A296853
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Expansion of e.g.f. tanh(x*tan(x/2)) (even powers only).
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6
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0, 1, 1, -27, -403, 8345, 688473, -208019, -3189211931, -162605047455, 28806493001105, 5257860587364341, -288068264497990179, -230932276247139756887, -14420179324444754436023, 13944106915630111553887485, 3643613240568912544562868053
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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) = (2*n)! * [x^(2*n)] tanh(x*tan(x/2)).
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EXAMPLE
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tanh(x*tan(x/2)) = x^2/2! + x^4/4! - 27*x^6/6! - 403*x^8/8! + 8345*x^10/10! + ...
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MATHEMATICA
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nmax = 16; Table[(CoefficientList[Series[Tanh[x Tan[x/2]], {x, 0, 2 nmax}], x] Range[0, 2 nmax]!)[[n]], {n, 1, 2 nmax + 1, 2}]
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CROSSREFS
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KEYWORD
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sign
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AUTHOR
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STATUS
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approved
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