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A012730 tan(arctanh(x)*arctan(x))=2/2!*x^2+448/6!*x^6+2138112/10!*x^10... 0
2, 448, 2138112, 53551718400, 4262315839979520, 826978943730607718400, 331594807758028302723317760, 245412719115132295441404238233600, 308745457206861968420290988707864903680, 620129923454446057412994114512456319793889280 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,1

LINKS

Table of n, a(n) for n=0..9.

MATHEMATICA

With[{nn=40}, Take[CoefficientList[Series[Tan[ArcTanh[x]ArcTan[x]], {x, 0, nn}], x] Range[0, nn-2]!, {3, -1, 4}]] (* Harvey P. Dale, Sep 24 2013 *)

CROSSREFS

Sequence in context: A200951 A118710 A159513 * A012734 A099686 A066152

Adjacent sequences: A012727 A012728 A012729 * A012731 A012732 A012733

KEYWORD

nonn

AUTHOR

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

EXTENSIONS

Definition clarified by and more terms from Harvey P. Dale, Sep 24 2013

STATUS

approved

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Last modified February 1 18:22 EST 2023. Contains 359995 sequences. (Running on oeis4.)