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A012680 arctan(tanh(x)*arctan(x))=2/2!*x^2-16/4!*x^4+80/6!*x^6+14464/8!*x^8... 0
0, 2, -16, 80, 14464, -1682432, 76011520, 26175092736, -10889734127616, 1790915255599104, 628448342217064448, -708415309969044275200, 277815404352915818676224, 89144743290434384702734336 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Table of n, a(n) for n=0..13.

MATHEMATICA

With[{nn=30}, Take[CoefficientList[Series[ArcTan[Tanh[x]*ArcTan[x]], {x, 0, nn}], x] Range[0, nn]!, {1, -1, 2}]] (* Ray Chandler, Nov 28 2016 *)

CROSSREFS

Sequence in context: A225959 A336174 A045905 * A012684 A234004 A053587

Adjacent sequences:  A012677 A012678 A012679 * A012681 A012682 A012683

KEYWORD

sign

AUTHOR

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

STATUS

approved

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Last modified November 28 04:16 EST 2020. Contains 338699 sequences. (Running on oeis4.)