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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
OFFSET
0,2
LINKS
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
KEYWORD
nonn,frac
AUTHOR
N. J. A. Sloane, May 05 2011
STATUS
approved