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A012193 sech(arctan(sin(x)))=1-1/2!*x^2+17/4!*x^4-721/6!*x^6+58337/8!*x^8... 2
1, -1, 17, -721, 58337, -7657441, 1482169457, -396854618161, 140415423261377, -63432792091634881, 35619694647751942097, -24334169873267896659601, 19872330538404158435859617 (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[ArcTan[Sin[x]]], {x, 0, nn}], x] Range[0, nn]!, {1, -1, 2}]] (* Harvey P. Dale, Jun 06 2018 *)

CROSSREFS

Sequence in context: A201311 A012182 A012029 * A128274 A012085 A298306

Adjacent sequences:  A012190 A012191 A012192 * A012194 A012195 A012196

KEYWORD

sign

AUTHOR

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

STATUS

approved

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Last modified February 21 15:11 EST 2019. Contains 320374 sequences. (Running on oeis4.)