A012809 tanh(sec(x)*arctan(x))=x-1/3!*x^3+25/5!*x^5-1209/7!*x^7+68945/9!*x^9...

1, -1, 25, -1209, 68945, -7692881, 1181481769, -242740782153, 66317255314721, -22739603323053601, 9634203397240829625, -4937246969845634306905, 3007627322996781467655025, -2149125294837930108279760753, 1779707247211878394671148764873

Offset

0,3

Links

Table of n, a(n) for n=0..14.

Mathematica

With[{nn=40}, Take[CoefficientList[Series[Tanh[Sec[x]ArcTan[x]], {x, 0, nn}], x] Range[0, nn-1]!, {2, -1, 2}]] (* Harvey P. Dale, Dec 29 2013 *)

Crossrefs

Sequence in context: A112102 A012799 A120694 * A014769 A012851 A395275

Adjacent sequences: A012806 A012807 A012808 * A012810 A012811 A012812

Keyword

sign

Author

Patrick Demichel

Extensions

More terms from Harvey P. Dale, Dec 29 2013

Status

approved