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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 Cf. A000182, A003718, A009707, A024257. Sequence in context: A304798 A154908 A166356 * A124105 A079613 A091299 Adjacent sequences: A009814 A009815 A009816 * A009818 A009819 A009820 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.)