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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 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 LINKS 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 * A012030 A012682 A012678 Adjacent sequences:  A009697 A009698 A009699 * A009701 A009702 A009703 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

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Last modified November 28 05:17 EST 2020. Contains 338699 sequences. (Running on oeis4.)