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A013519
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Numerator of [x^(2n+1)] in the Taylor expansion tan(cosec(x)-cot(x)).
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1
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1, 1, 3, 181, 59, 3455, 3332389, 173339393, 449509681, 198232237033, 1032475444411, 101635950910031, 71432133543444211, 671713726985602398481
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OFFSET
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0,3
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COMMENTS
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The e.g.f. of x/2, tan(cosec(x)-cot(x)) = x/(2^1*1!) + 4*x^3/(2^3*3!) +72*x^5/(2^5*5!) + 2896*x^7/(2^7*7!) +.. is apparently covered by A003718.
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LINKS
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EXAMPLE
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x/2 +x^3/12 +3*x^5/160 +181*x^7/40320 +59*x^9/53760 +3455*x^11/12773376 +...
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MATHEMATICA
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Numerator[Take[CoefficientList[Series[Tan[Csc[x] - Cot[x]], {x, 0, 25}], x], {2, -1, 2}]] (* G. C. Greubel, Nov 12 2016 *)
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CROSSREFS
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KEYWORD
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nonn,frac
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AUTHOR
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Patrick Demichel (patric.demichel(AT)hp.com)
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EXTENSIONS
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STATUS
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approved
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