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 A009089 Expansion of e.g.f. cos(tanh(x))/cos(x), even powers only. 1
 1, 0, 8, -56, 3968, -133248, 13993088, -1139191808, 178943504384, -26439024316416, 5943319707680768, -1368130407134953472, 421233393478948782080, -137934416762714295631872, 56032481949750675250085888 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 LINKS G. C. Greubel, Table of n, a(n) for n = 0..239 MAPLE seq(coeff(series(factorial(n)*cos(tanh(x))/cos(x), x, n+1), x, n), n=0..30, 2); # Muniru A Asiru, Jul 25 2018 MATHEMATICA With[{nn=30}, Take[CoefficientList[Series[Cos[Tanh[x]]/Cos[x], {x, 0, nn}], x] Range[0, nn]!, {1, -1, 2}]] (* Harvey P. Dale, Jul 14 2018 *) PROG (PARI) x='x+O('x^50); v=Vec(serlaplace(cos(tanh(x))/cos(x))); vector(#v\2, n, v[2*n-1]) \\ G. C. Greubel, Jul 25 2018 CROSSREFS Sequence in context: A326239 A154411 A105850 * A296466 A202863 A244958 Adjacent sequences:  A009086 A009087 A009088 * A009090 A009091 A009092 KEYWORD sign AUTHOR EXTENSIONS Extended with signs by Olivier Gérard, Mar 15 1997 Prior Mathematica program replaced by Harvey P. Dale, Jul 14 2018 STATUS approved

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Last modified January 17 22:33 EST 2022. Contains 350410 sequences. (Running on oeis4.)