A013534 - OEIS

%I #17 Nov 13 2016 06:57:36

%S 1,-1,1,-5029,6697,-375719873,186044689,-1770350411,102625697881591,

%T -15912188224095499151,1419184560088744177499,

%U -323645955378411578735051,935339682040604214800761,-36813244507954712597112169117,45816041290074218754101655557981

%N Numerator of [x^(2n)] in the Taylor expansion cos(cosec(x) - cosech(x)).

%C Essentially a bisection of A013529.

%H G. C. Greubel, <a href="/A013534/b013534.txt">Table of n, a(n) for n = 0..200</a>

%e 1 - x^2/18 + x^4/1944 - 5029*x^6/3674160 + 6697*x^8/264539520 - ...

%t Numerator[Take[CoefficientList[Series[Cos[Csc[x] - Csch[x]], {x,0,25}], x], {1, -1, 2}]] (* _G. C. Greubel_, Nov 12 2016 *)

%Y Cf. A068917.

%K sign,frac

%O 0,4

%A Patrick Demichel (patrick.demichel(AT)hp.com)

%E Name edited by _R. J. Mathar_, Dec 20 2011