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Denominators of Taylor series for exp(x)*cos(x).
6

%I #13 Feb 14 2014 21:07:15

%S 1,1,1,3,6,30,1,630,2520,22680,1,1247400,7484400,97297200,1,

%T 10216206000,81729648000,1389404016000,1,237588086736000,

%U 2375880867360000,49893498214560000,1,12623055048283680000,151476660579404160000,3786916514485104000000

%N Denominators of Taylor series for exp(x)*cos(x).

%D G. W. Caunt, Infinitesimal Calculus, Oxford Univ. Press, 1914, p. 477.

%H T. D. Noe, <a href="/A046981/b046981.txt">Table of n, a(n) for n=0..100</a>

%F a(4n+2) = 1, a(n) = n!/2^[n/2].

%e 1+1*x-1/3*x^3-1/6*x^4-1/30*x^5+1/630*x^7+1/2520*x^8+1/22680*x^9-...

%t Denominator/@CoefficientList[Series[Exp[x]Cos[x],{x,0,30}],x] (* _Harvey P. Dale_, Jun 28 2011 *)

%Y Cf. A046980, A046979, A052277, A007019, A007415, A009775, A092820.

%Y Absolute values are essentially the same as A007452.

%K nonn,frac,easy,nice

%O 0,4

%A _N. J. A. Sloane_