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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
OFFSET
0,3
LINKS
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
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