A067655 Denominators of the coefficients in exp(2x/(1-x)) power series.

1, 1, 3, 3, 15, 45, 315, 315, 2835, 14175, 155925, 467775, 6081075, 3869775, 638512875, 638512875, 10854718875, 8881133625, 1856156927625, 9280784638125, 194896477400625, 2143861251406875, 2595200462229375

Offset: 1

Author

Benoit Cloitre, Feb 03 2002

Keywords

• nonn
• frac

Comments

Differs from A049606 at positions enumerated by A097324.

References

• K. Knopp, Theory and application of infinite series, Dover, p. 547.
• O. Perron, Über das infinitäre Verhalten der Koeffizienten einer gewissen Potenzreihe, Archiv d. Math. u. Phys. (3), Vol. 22, pp. 329-340, 1914.

Crossrefs

Cf. A067654.

Formula

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