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A009700
Expansion of tan(tan(x))*x.
1
0, 2, 16, 432, 23168, 2039040, 265344000, 47773128704, 11359970459648, 3446710775119872, 1299134788619468800, 595445934379289804800, 326113437715996197519360, 210324874581761164037849088
OFFSET
0,2
FORMULA
a(n) ~ (2*n)! * 8 / ((4+Pi^2) * arctan(Pi/2)^(2*n)). - Vaclav Kotesovec, Jan 23 2015
MATHEMATICA
With[{nn=30}, Take[CoefficientList[Series[Tan[Tan[x]]*x , {x, 0, nn}], x] Range[0, nn]!, {1, -1, 2}]] (* Harvey P. Dale, Jun 08 2014 *)
CROSSREFS
Sequence in context: A282309 A009397 A229023 * A358784 A012030 A012682
KEYWORD
nonn
AUTHOR
EXTENSIONS
Extended and signs tested Mar 15 1997 by Olivier Gérard.
Previous Mathematica program replaced by Harvey P. Dale, Jun 08 2014
STATUS
approved