A053485 Denominators in expansion of exp(2x)/(1-x).

1, 1, 1, 3, 1, 15, 45, 21, 315, 2835, 4725, 22275, 93555, 2027025, 42567525, 638512875, 212837625, 2170943775, 13956067125, 618718975875, 9280784638125, 14992036723125, 7522320180375, 49308808782358125, 147926426347074375

Offset: 0

Author

N. J. A. Sloane, Jan 15 2000

Keywords

• nonn
• frac

Links

• G. C. Greubel, Table of n, a(n) for n = 0..400

Crossrefs

Cf. A053484, A010842.

Programs

Mathematica

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

PARI

for(n=0,25, print1(denominator(sum(k=0,n, 2^k/k!)), ", ")) \\ G. C. Greubel, Jan 18 2017

Formula

a(n) = denominator( Sum_{k=0..n} 2^k/k! ). - G. C. Greubel, Jan 18 2017