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A012687
sech(tanh(x)*arctan(x))=1-12/4!*x^4+480/6!*x^6-18480/8!*x^8...
0
1, 0, -12, 480, -18480, 176640, 149396544, -38742692352, 6743113079040, -363222941859840, -455485254371044352, 322516524038804660224, -135316725169663246512128, 19655917963465137568481280
OFFSET
0,3
MATHEMATICA
With[{nn=30}, Take[CoefficientList[Series[Sech[Tanh[x]ArcTan[x]], {x, 0, nn}], x] Range[0, nn]!, {1, -1, 2}]] (* Harvey P. Dale, Apr 19 2019 *)
CROSSREFS
Sequence in context: A241226 A003749 A012395 * A012467 A009083 A012681
KEYWORD
sign
AUTHOR
Patrick Demichel (patrick.demichel(AT)hp.com)
STATUS
approved