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A013448 sech(tan(x)-arctan(x))=1-160/6!*x^6+1792/8!*x^8-484224/10!*x^10... 0
1, 0, 0, -160, 1792, -484224, 54495232, -9441003520, 2598020579328, -756380393635840, 305071008569196544, -144297159065656885248, 81729693136918543335424, -55094722790449057575731200 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,4

LINKS

Table of n, a(n) for n=0..13.

MATHEMATICA

With[{nn=30}, Take[CoefficientList[Series[Sech[Tan[x]-ArcTan[x]], {x, 0, nn}], x] Range[0, nn]!, {1, -1, 2}]] (* Harvey P. Dale, Feb 04 2016 *)

CROSSREFS

Sequence in context: A013447 A013446 A013444 * A234650 A214354 A188306

Adjacent sequences:  A013445 A013446 A013447 * A013449 A013450 A013451

KEYWORD

sign

AUTHOR

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

STATUS

approved

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Last modified June 24 00:08 EDT 2021. Contains 345403 sequences. (Running on oeis4.)