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A024280 Expansion of tanh(tan(x)^2)/2. 0
0, 1, 8, 16, -9472, -1073024, -73802752, 6179501056, 4687080685568, 1381417658515456, 171579748064165888, -115606987957684404224, -118208590165253073928192, -59168959906143078642089984 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

LINKS

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

MATHEMATICA

With[{nn=30}, Take[CoefficientList[Series[Tanh[Tan[x]^2]/2, {x, 0, nn}], x] Range[0, nn]!, {1, -1, 2}]] (* Harvey P. Dale, Dec 31 2014 *)

CROSSREFS

Cf. A009819.

Sequence in context: A284438 A236285 A247850 * A115434 A024107 A234839

Adjacent sequences:  A024277 A024278 A024279 * A024281 A024282 A024283

KEYWORD

sign

AUTHOR

R. H. Hardin

EXTENSIONS

Extended with signs Mar 1997

Prior Mathematica program replaced by Harvey P. Dale, Dec 31 2014

STATUS

approved

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Last modified October 15 21:06 EDT 2018. Contains 316237 sequences. (Running on oeis4.)