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Denominators in expansion of exp(2x)/(1-x).
3

%I #8 Jan 19 2017 02:33:45

%S 1,1,1,3,1,15,45,21,315,2835,4725,22275,93555,2027025,42567525,

%T 638512875,212837625,2170943775,13956067125,618718975875,

%U 9280784638125,14992036723125,7522320180375,49308808782358125,147926426347074375

%N Denominators in expansion of exp(2x)/(1-x).

%H G. C. Greubel, <a href="/A053485/b053485.txt">Table of n, a(n) for n = 0..400</a>

%F a(n) = denominator( Sum_{k=0..n} 2^k/k! ). - _G. C. Greubel_, Jan 18 2017

%t Denominator[Table[Sum[2^k/k!, {k, 0, n}], {n, 0, 50}]] (* _G. C. Greubel_, Jan 18 2017 *)

%o (PARI) for(n=0,25, print1(denominator(sum(k=0,n, 2^k/k!)), ", ")) \\ _G. C. Greubel_, Jan 18 2017

%Y Cf. A053484, A010842.

%K nonn,frac

%O 0,4

%A _N. J. A. Sloane_, Jan 15 2000