A009094 - OEIS

A009094

Expansion of e.g.f. cos(tanh(x)*tan(x)) (only powers that are multiples of 4).

1, -12, -4592, -6274752, 18138366208, 2332645761266688, 202540305420145266688, 24977439274944176331767808, 4480212151308993274762821173248, 1107507319145672023044777103840247808, 336310686770623540666061200154740824997888

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OFFSET

0,2

LINKS

G. C. Greubel, Table of n, a(n) for n = 0..120

MATHEMATICA

With[{nn=60}, Select[CoefficientList[Series[Cos[Tanh[x]Tan[x]], {x, 0, nn}], x]Range[0, nn]!, #!=0&]] (* Harvey P. Dale, Dec 28 2012 *)

PROG

(PARI) x='x+O('x^80); v=Vec(serlaplace(cos(tanh(x)*tan(x)))); vector(#v\4, n, v[4*n-3]) \\ G. C. Greubel, Jul 25 2018

CROSSREFS

Sequence in context: A287889 A288967 A361106 * A061701 A236067 A134821

Adjacent sequences: A009091 A009092 A009093 * A009095 A009096 A009097

KEYWORD

sign

AUTHOR

R. H. Hardin

EXTENSIONS

Extended with signs by Olivier Gérard, Mar 15 1997

STATUS

approved