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A009770
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Expansion of tanh(log(1+log(1+x))).
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0
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0, 1, -2, 5, -11, -16, 656, -9066, 107766, -1222110, 13400544, -137979810, 1199045706, -4684987308, -153270916044, 6326220565560, -169975260810216, 3943603406845656, -83676044951653392, 1624994111075924376
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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) ~ n! * 2 * exp(n) * (-1)^(n+1) * ((sin(n*arctan(sin(1)/(cos(1) - exp(1)))) + exp(1)*sin(1 - n*arctan(sin(1)/(cos(1) - exp(1))))) / (1 + exp(2) - 2*exp(1)*cos(1))^(1 + n/2)). - Vaclav Kotesovec, Jan 24 2015
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MATHEMATICA
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Tanh[ Log[ 1+Log[ 1+x ] ] ]
CoefficientList[Series[1 - 2/(2 + Log[1 + x]*(2 + Log[1 + x])), {x, 0, 20}], x] * Range[0, 20]! (* Vaclav Kotesovec, Jan 24 2015 *)
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CROSSREFS
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KEYWORD
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sign,easy
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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