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A009817 Expansion of e.g.f. tanh(tan(x)*x) (even powers only). 3
0, 2, 8, -144, -11264, -323840, 36347904, 8388294656, 620426657792, -168731721990144, -79627879039631360, -11099857853570613248, 5627175549005859913728, 4469405304978356270268416 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,2
LINKS
Iain Fox, Table of n, a(n) for n = 0..231 (first 101 terms from Vincenzo Librandi)
MAPLE
S:= series(tanh(tan(x)*x), x, 41):
seq(coeff(S, x, n)*n!, n=0..40, 2); # Robert Israel, Dec 21 2017
MATHEMATICA
With[{nn=30}, Take[CoefficientList[Series[Tanh[Tan[x]*x], {x, 0, nn}], x] Range[0, nn]!, {1, -1, 2}]] (* Harvey P. Dale, Oct 28 2013 *)
PROG
(PARI) first(n) = x='x+O('x^(2*n-1)); vecextract(Vec(serlaplace(tanh(tan(x)*x)), -2*n), (4^n - 1)/3) \\ Iain Fox, Dec 21 2017
CROSSREFS
Sequence in context: A304798 A154908 A166356 * A124105 A079613 A091299
KEYWORD
sign
AUTHOR
R. H. Hardin, Mar 15 1996
EXTENSIONS
Extended with signs by Olivier Gérard, Mar 15 1997
Prior Mathematica program replaced by Harvey P. Dale, Oct 28 2013
STATUS
approved

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Last modified July 17 14:36 EDT 2024. Contains 374377 sequences. (Running on oeis4.)