A012730 tan(arctanh(x)*arctan(x))=2/2!*x^2+448/6!*x^6+2138112/10!*x^10...

2, 448, 2138112, 53551718400, 4262315839979520, 826978943730607718400, 331594807758028302723317760, 245412719115132295441404238233600, 308745457206861968420290988707864903680, 620129923454446057412994114512456319793889280

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 A363699 A099686

Adjacent sequences: A012727 A012728 A012729 * A012731 A012732 A012733

Keyword

nonn

Author

Patrick Demichel

Extensions

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

Status

approved