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A012692 sech(tanh(x)*cos(x))=1-1/2!*x^2+25/4!*x^4-1057/6!*x^6+81905/8!*x^8... 0
1, -1, 25, -1057, 81905, -10280289, 1887120585, -476966767617, 158890850697185, -67468163508862017, 35571148438980847225, -22799419589275221917281, 17459463801481355245128145 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

LINKS

Table of n, a(n) for n=0..12.

MATHEMATICA

With[{nn=30}, Take[CoefficientList[Series[Sech[Tanh[x]Cos[x]], {x, 0, nn}], x] Range[0, nn]!, {1, -1, 2}]] (* Harvey P. Dale, Apr 13 2019 *)

CROSSREFS

Sequence in context: A232698 A139163 A167257 * A193121 A246923 A066852

Adjacent sequences:  A012689 A012690 A012691 * A012693 A012694 A012695

KEYWORD

sign

AUTHOR

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

STATUS

approved

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Last modified January 23 21:56 EST 2022. Contains 350515 sequences. (Running on oeis4.)