A012806 - OEIS

A012806

cos(sec(x)*arctan(x))=1-1/2!*x^2-3/4!*x^4-165/6!*x^6+1337/8!*x^8...

1, -1, -3, -165, 1337, -356745, 31874997, -5714452653, 1296863374193, -357091592679441, 131690816886952045, -56304582100478416309, 29876409015019700748969, -18379375710670502969514905

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OFFSET

0,3

LINKS

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

MATHEMATICA

With[{nn=30}, Take[CoefficientList[Series[Cos[Sec[x]ArcTan[x]], {x, 0, nn}], x] Range[0, nn]!, {1, -1, 2}]] (* Harvey P. Dale, Jul 24 2017 *)

CROSSREFS

Sequence in context: A285488 A112896 A185242 * A020545 A228193 A297820

Adjacent sequences: A012803 A012804 A012805 * A012807 A012808 A012809

KEYWORD

sign

AUTHOR

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

STATUS

approved