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A112103 Denominator of Sum_{i=1..n} 1/(i^3*C(2*i,i)). 4
1, 2, 48, 2160, 120960, 3024000, 99792000, 63567504000, 46230912000, 77806624896000, 4548694993920, 7155097225436160, 164567236185031680, 139059314576351769600, 139059314576351769600, 100818003067855032960000, 25002864760828048174080000 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Table of n, a(n) for n=0..16.

C. Elsner, On recurrence formulas for sums involving binomial coefficients, Fib. Q., 43,1 (2005), 31-45.

EXAMPLE

0, 1/2, 25/48, 1129/2160, 63251/120960, 1581371/3024000, 52185743/99792000, ... -> Pi^2/18.

PROG

(PARI) a(n) = denominator(sum(i=1, n, 1/(i^3*binomial(2*i, i)))); \\ Michel Marcus, Mar 10 2016

CROSSREFS

Cf. A112102.

Sequence in context: A186284 A119695 A119698 * A177317 A114714 A186416

Adjacent sequences:  A112100 A112101 A112102 * A112104 A112105 A112106

KEYWORD

nonn,frac

AUTHOR

N. J. A. Sloane, Nov 30 2005

EXTENSIONS

Definition corrected (and an incorrect sum deleted) by Wolfdieter Lang, Oct 07 2008

STATUS

approved

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Last modified September 20 16:50 EDT 2021. Contains 347586 sequences. (Running on oeis4.)