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%I #22 Sep 19 2023 09:14:18
%S 1,4,96,5760,645120,16588800,30656102400,11158821273600,
%T 109310902272000,3278015337332736000,191637819720990720000,
%U 25296192203170775040000,2541356653499348743618560000,3303763649549153366704128000000,713612948302617127208091648000000
%N Denominators of a Taylor series expansion of 1/sqrt(cosh(x)) (even powers only).
%H Vincenzo Librandi, <a href="/A190196/b190196.txt">Table of n, a(n) for n = 0..100</a>
%H Philippe Flajolet, Xavier Gourdon, and Philippe Dumas, <a href="https://doi.org/10.1016/0304-3975(95)00002-E">Mellin transforms and asymptotics: harmonic sums</a>, Special volume on mathematical analysis of algorithms. Theoret. Comput. Sci. 144 (1995), no. 1-2, 3-58.
%e 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+...
%p a:= n-> denom(coeff(series(1/sqrt(cosh(x)),x,2*n+1),x,2*n)):
%p seq(a(n), n=0..19); # _Alois P. Heinz_, Sep 19 2023
%t Denominator[Take[CoefficientList[Series[1/Sqrt[Cosh[x]],{x,0,40}],x],{1,-1,2}]] (* _Harvey P. Dale_, Feb 04 2012 *)
%Y Cf. A190195.
%K nonn,frac
%O 0,2
%A _N. J. A. Sloane_, May 05 2011
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