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A012805 arctan(sec(x)*arctan(x))=x-1/3!*x^3+33/5!*x^5-1377/7!*x^7+99649/9!*x^9... 0
1, -1, 33, -1377, 99649, -11796673, 2017677153, -471591223841, 144742585812609, -56447611418620289, 27268126498786597537, -15985843319019939868385, 11182140682997302960743361 (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[ArcTan[Sec[x]*ArcTan[x]], {x, 0, nn}], x] Range[0, nn-1]!, {2, -1, 2}]] (* Ray Chandler, Nov 28 2016 *)

CROSSREFS

Sequence in context: A242492 A065424 A071268 * A093756 A284333 A284198

Adjacent sequences:  A012802 A012803 A012804 * A012806 A012807 A012808

KEYWORD

sign

AUTHOR

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

STATUS

approved

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Last modified August 12 11:44 EDT 2020. Contains 336439 sequences. (Running on oeis4.)