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A012675
sech(tanh(x)*tan(x))=1-12/4!*x^4+2128/8!*x^8+3482688/12!*x^12...
0
1, -12, 2128, 3482688, -28510476032, -29203453996032, 18429307563035250688, -709977989050867131727872, -146234048852276431866584563712, 20573909798214617779391304930951168
OFFSET
0,2
MATHEMATICA
With[{nn=40}, Take[CoefficientList[Series[Sech[Tanh[x]Tan[x]], {x, 0, nn}], x] Range[0, nn]!, {1, -2, 4}]] (* Harvey P. Dale, Sep 10 2019 *)
CROSSREFS
Sequence in context: A004823 A342964 A009063 * A175014 A101812 A064074
KEYWORD
sign
AUTHOR
Patrick Demichel (patrick.demichel(AT)hp.com)
EXTENSIONS
More terms from Harvey P. Dale, Sep 10 2019
STATUS
approved