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%I #17 Jul 26 2018 08:04:52
%S 1,0,-8,56,512,-54912,2590336,-69311488,-3936710656,914002857984,
%T -81770855727104,-2175764106870784,2405710131432685568,
%U -359158536158603378688,-106865524988327138951168
%N Expansion of e.g.f. cos(x)/cos(tanh(x)), even powers only.
%H G. C. Greubel, <a href="/A009107/b009107.txt">Table of n, a(n) for n = 0..242</a>
%t With[{nmax = 60}, CoefficientList[Series[Cos[x]/Cos[Tanh[x]], {x, 0, nmax}], x]*Range[0, nmax]!][[1 ;; -1 ;; 2]] (* _G. C. Greubel_, Jul 26 2018 *)
%o (PARI) x='x+O('x^50); v=Vec(serlaplace(cos(x)/cos(tanh(x)))); vector(#v\2,n,v[2*n-1]) \\ _G. C. Greubel_, Jul 26 2018
%Y Cf. A009297.
%K sign
%O 0,3
%A _R. H. Hardin_
%E Extended with signs by _Olivier Gérard_, Mar 15 1997
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