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Denominators of the coefficients in exp(2x/(1-x)) power series.
3

%I #15 Feb 02 2019 14:14:10

%S 1,1,3,3,15,45,315,315,2835,14175,155925,467775,6081075,3869775,

%T 638512875,638512875,10854718875,8881133625,1856156927625,

%U 9280784638125,194896477400625,2143861251406875,2595200462229375

%N Denominators of the coefficients in exp(2x/(1-x)) power series.

%C Differs from A049606 at positions enumerated by A097324.

%D K. Knopp, Theory and application of infinite series, Dover, p. 547.

%D O. Perron, Über das infinitäre Verhalten der Koeffizienten einer gewissen Potenzreihe, Archiv d. Math. u. Phys. (3), Vol. 22, pp. 329-340, 1914.

%F a(n) is the denominator in Sum_{i=1..n} binomial(n-1, i-1)*2^i/i!.

%Y Cf. A067654.

%K nonn,frac

%O 1,3

%A _Benoit Cloitre_, Feb 03 2002