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A012737
sech(arctanh(x)*arctan(x))=1-12/4!*x^4-3248/8!*x^8-25240512/12!*x^12...
0
1, -12, -3248, -25240512, -722745554688, -61363036297915392, -12105663188188359045120, -4791193110632356981925068800
OFFSET
0,2
MATHEMATICA
With[{nn=34}, Take[CoefficientList[Series[Sech[ArcTanh[x]*ArcTan[x]], {x, 0, nn}], x] Range[0, nn-2]!, {1, -1, 4}]] (* Ray Chandler, Nov 28 2016 *)
CROSSREFS
Sequence in context: A268048 A271516 A012603 * A370298 A077299 A077749
KEYWORD
sign
AUTHOR
Patrick Demichel (patrick.demichel(AT)hp.com)
STATUS
approved