A013534 Numerator of [x^(2n)] in the Taylor expansion cos(cosec(x) - cosech(x)).

1, -1, 1, -5029, 6697, -375719873, 186044689, -1770350411, 102625697881591, -15912188224095499151, 1419184560088744177499, -323645955378411578735051, 935339682040604214800761, -36813244507954712597112169117, 45816041290074218754101655557981

Offset

0,4

Comments

Essentially a bisection of A013529.

Links

G. C. Greubel, Table of n, a(n) for n = 0..200

Example

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

Mathematica

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

Crossrefs

Cf. A068917.

Sequence in context: A188241 A252162 A248986 * A309034 A237690 A290121

Adjacent sequences: A013531 A013532 A013533 * A013535 A013536 A013537

Keyword

sign,frac

Author

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

Extensions

Name edited by R. J. Mathar, Dec 20 2011

Status

approved