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A009080 Expansion of e.g.f. cos(x*tan(x)), even terms only. 2

%I

%S 1,0,-12,-240,-5936,-155520,-65472,981903104,223580862720,

%T 46255608778752,10060678641587200,2368138744630923264,

%U 601490101481648443392,161192778898870464512000,43208403753541588946141184

%N Expansion of e.g.f. cos(x*tan(x)), even terms only.

%H G. C. Greubel, <a href="/A009080/b009080.txt">Table of n, a(n) for n = 0..240</a>

%e cos(x*tan(x)) = 1/0! +0*x^2/2! -12*x^4/4! -240*x^6/6! -5936*x^8/8! -...

%t With[{nmax = 60}, CoefficientList[Series[Cos[x*Tan[x]], {x, 0, nmax}], x]*Range[0, nmax]!][[1 ;; -1 ;; 2]] (* _G. C. Greubel_, Jul 24 2018 *)

%o (PARI) x='x+O('x^60); v=Vec(serlaplace(cos(x*tan(x)))); vector(#v\2,n,v[2*n-1]) \\ _G. C. Greubel_, Jul 24 2018

%K sign

%O 0,3

%A _R. H. Hardin_

%E Extended with signs by _Olivier GĂ©rard_, Mar 15 1997

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Last modified May 8 07:02 EDT 2021. Contains 343653 sequences. (Running on oeis4.)