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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

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

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

R. H. Hardin

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.)