A012615 cos(arcsinh(x)*tan(x))=1-12/4!*x^4-120/6!*x^6-5040/8!*x^8...

1, 0, -12, -120, -5040, -35520, -10080576, 1291774848, -129155669760, 70025050601472, -12621771155397632, 7717419122045659136, -2918362206037173678080, 1928021073359516653240320, -1209535003923466323711246336, 977832736949625091059703971840

Offset

0,3

Links

Table of n, a(n) for n=0..15.

Formula

a(n) ~ (-1)^(n+1) * sin(Pi*tanh(1)/2) * tanh(1) * 2^(2*n) * n^(2*n-1) / exp(2*n). - Vaclav Kotesovec, Oct 31 2013

Mathematica

Table[n!*SeriesCoefficient[Cos[ArcSinh[x]*Tan[x]], {x, 0, n}], {n, 0, 40, 2}] (* Vaclav Kotesovec, Oct 31 2013 *)
With[{nn=30}, Take[CoefficientList[Series[Cos[ArcSinh[x]Tan[x]], {x, 0, nn}], x] Range[0, nn]!, {1, -1, 2}]]

Crossrefs

Sequence in context: A009149 A010570 A012374 * A012559 A009164 A012436

Adjacent sequences: A012612 A012613 A012614 * A012616 A012617 A012618

Keyword

sign

Author

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

Extensions

More terms from Harvey P. Dale, Dec 16 2017

Status

approved