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A009043 Expansion of cos(sin(x))/cos(x), even terms only. 1

%I #14 Jul 24 2018 02:58:17

%S 1,0,4,24,848,25792,1491392,106879616,10504954112,1298259085312,

%T 200164547589120,37466482286032896,8382720548500262912,

%U 2208241619066995294208,676599830605856131694592

%N Expansion of cos(sin(x))/cos(x), even terms only.

%H G. C. Greubel, <a href="/A009043/b009043.txt">Table of n, a(n) for n = 0..242</a>

%F a(n) ~ (2*n)! * cos(1) * 4^(n+1) / Pi^(2*n+1). - _Vaclav Kotesovec_, Jan 22 2015

%t nn = 20; Table[(CoefficientList[Series[Cos[Sin[x]]*Sec[x], {x, 0, 2*nn}], x] * Range[0, 2*nn]!)[[n]], {n, 1, 2*nn+1, 2}] (* _Vaclav Kotesovec_, Jan 22 2015 *)

%o (PARI) x='x+O('x^50); v=Vec(serlaplace(cos(sin(x))/cos(x))); vector(#v\2,n,v[2*n-1]) \\ _G. C. Greubel_, Jul 23 2018

%K nonn

%O 0,3

%A _R. H. Hardin_

%E Extended and signs tested Mar 15 1997 by _Olivier GĂ©rard_.

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Last modified February 23 06:06 EST 2024. Contains 370267 sequences. (Running on oeis4.)