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 A190196 Denominators of a Taylor series expansion of 1/sqrt(cosh(x)) (even powers only). 2
 1, 4, 96, 5760, 645120, 16588800, 30656102400, 11158821273600, 109310902272000, 3278015337332736000, 191637819720990720000, 25296192203170775040000, 2541356653499348743618560000, 3303763649549153366704128000000, 713612948302617127208091648000000 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 LINKS Vincenzo Librandi, Table of n, a(n) for n = 0..100 Philippe Flajolet, Xavier Gourdon, and Philippe Dumas, Mellin transforms and asymptotics: harmonic sums, Special volume on mathematical analysis of algorithms. Theoret. Comput. Sci. 144 (1995), no. 1-2, 3-58. EXAMPLE 1/sqrt(cosh(x)) = 1-(1/4)*x^2+(7/96)*x^4-(139/5760)*x^6+(5473/645120)*x^8-(51103/16588800)*x^10+... MAPLE a:= n-> denom(coeff(series(1/sqrt(cosh(x)), x, 2*n+1), x, 2*n)): seq(a(n), n=0..19); # Alois P. Heinz, Sep 19 2023 MATHEMATICA Denominator[Take[CoefficientList[Series[1/Sqrt[Cosh[x]], {x, 0, 40}], x], {1, -1, 2}]] (* Harvey P. Dale, Feb 04 2012 *) CROSSREFS Cf. A190195. Sequence in context: A062779 A077155 A013042 * A065140 A007106 A111637 Adjacent sequences: A190193 A190194 A190195 * A190197 A190198 A190199 KEYWORD nonn,frac,changed AUTHOR N. J. A. Sloane, May 05 2011 STATUS approved

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Last modified October 2 07:08 EDT 2023. Contains 365831 sequences. (Running on oeis4.)