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A046979
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Denominators of Taylor series for exp(x)*sin(x).
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7
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1, 1, 1, 3, 1, 30, 90, 630, 1, 22680, 113400, 1247400, 1, 97297200, 681080400, 10216206000, 1, 1389404016000, 12504636144000, 237588086736000, 1, 49893498214560000, 548828480360160000, 12623055048283680000, 1, 3786916514485104000000, 49229914688306352000000
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OFFSET
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0,4
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REFERENCES
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G. W. Caunt, Infinitesimal Calculus, Oxford Univ. Press, 1914, p. 477.
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LINKS
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FORMULA
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a(4n) = 1, a(n) = n!/2^floor(n/2).
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EXAMPLE
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1*x + 1*x^2 + 1/3*x^3 - 1/30*x^5 - 1/90*x^6 - 1/630*x^7 + 1/22680*x^9 + 1/113400*x^10 + ...
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MAPLE
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a:= n-> denom(coeff(series(sin(x)/exp(x), x, n+1), x, n)):
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MATHEMATICA
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Denominator[CoefficientList[Series[Exp[x]Sin[x], {x, 0, 30}], x] ] (* Harvey P. Dale, Feb 14 2015 *)
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PROG
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(PARI) a(n) = if (n % 4, n!/2^floor(n/2), 1); \\ Michel Marcus, Oct 12 2015
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CROSSREFS
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Essentially the same as absolute values of A007415.
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KEYWORD
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nonn,frac,easy,nice
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AUTHOR
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STATUS
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approved
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