A213069 Expansion of e.g.f. arcsinh(cos(x)*sech(x)), even powers only.

0, -1, 3, -1, -77, -13921, 791043, 23892959, -3518362637, -801110007361, 149920222346883, 24069808471917119, -7334638751184472397, -2673575321959933341601, 1059696929013386749787523, 413637485668406346391368479

Offset

0,3

Comments

This function is even, with constant term arcsinh(1) = 0.881373587019543...

Links

Vincenzo Librandi, Table of n, a(n) for n = 0..100

Formula

E.g.f.: (arcsinh(cos(x)*sech(x))-arcsinh(1))/sqrt(2).

Example

(arcsinh(cos(x)*sech(x))-arcsinh(1))/sqrt(2) = -x^2/2 + 3*x^4/4! - x^6/6! - 77*x^8/8! + ...

Mathematica

Part[#, Range[1, Length[#], 2]] &@(Array[#! &, Length[#], 0]*#) &@ CoefficientList[Series[(ArcSinh[Cos[x]*Sech[x]] - ArcSinh[1])/Sqrt[2], {x, 0, 30}], x] // ExpandAll
With[{nn=30}, Take[CoefficientList[Series[(ArcSinh[Cos[x]Sech[x]]-ArcSinh[ 1])/ Sqrt[2], {x, 0, nn}], x]Range[0, nn]!, {1, -1, 2}]] (* Harvey P. Dale, Mar 24 2013 *)

Crossrefs

Cf. A213066, A213067, A213068.

Sequence in context: A213127 A361091 A344050 * A357813 A266277 A016482

Adjacent sequences: A213066 A213067 A213068 * A213070 A213071 A213072

Keyword

sign

Author

Olivier Gérard, Jun 04 2012

Status

approved