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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
OFFSET
0,3
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: A375103 A236285 A247850 * A115434 A024107 A234839
KEYWORD
sign
AUTHOR
EXTENSIONS
Extended with signs Mar 1997
Prior Mathematica program replaced by Harvey P. Dale, Dec 31 2014
STATUS
approved