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A013179 cos(arctanh(x)+arctan(x))=1-4/2!*x^2+16/4!*x^4-640/6!*x^6+21760/8!*x^8... 0
1, -4, 16, -640, 21760, -2291200, 223436800, -44438118400, 8725110784000, -2796896567296000, 926039081943040000, -435519369139978240000, 218626979887002419200000, -141711151230417633280000000 (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[Cos[ArcTanh[x]+ArcTan[x]], {x, 0, nn}], x] Range[0, nn]!, {1, -1, 2}]] (* Ray Chandler, Nov 29 2016 *)

CROSSREFS

Sequence in context: A013006 A013001 A218644 * A144177 A300315 A296628

Adjacent sequences:  A013176 A013177 A013178 * A013180 A013181 A013182

KEYWORD

sign

AUTHOR

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

STATUS

approved

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Last modified November 29 18:41 EST 2021. Contains 349416 sequences. (Running on oeis4.)