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A012466 E.g.f. sec(arctan(x)^2) (even powers only). 1
1, 0, 12, -480, 37968, -4773120, 878319552, -222512349696, 74262725323008, -31578556041732096, 16666719859336276992, -10690478515516973015040, 8190555666463900906475520, -7387658525325188387856384000 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

LINKS

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

EXAMPLE

sec(arctan(x)^2) = =1+12/4!*x^4-480/6!*x^6+37968/8!*x^8+-...

MATHEMATICA

With[{nn=30}, Take[CoefficientList[Series[Sec[ArcTan[x]^2], {x, 0, nn}], x]Range[0, nn]!, {1, -1, 2}]] (* Harvey P. Dale, Jan 12 2013 *)

CROSSREFS

Sequence in context: A012465 A012394 A012686 * A229634 A196704 A175322

Adjacent sequences:  A012463 A012464 A012465 * A012467 A012468 A012469

KEYWORD

sign

AUTHOR

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

STATUS

approved

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Last modified October 14 08:54 EDT 2019. Contains 327995 sequences. (Running on oeis4.)