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 A084224 Denominators of successive approximations to zeta(3) = Sum_{k>0} 1/k^3, using Zeilberger's formula with s=2. 2
 24, 1728, 324000, 19559232000, 208039104000, 181050031008000, 1889392861091736000, 32719838723847475200, 126909921829154720256000, 25243779460958994560841216000 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS G. C. Greubel, Table of n, a(n) for n = 1..328 D. Zeilberger, Faster and Faster convergent series for zeta(3), arXiv:math/9804126 [math.CO], 1998. FORMULA a(n) = denominator( Sum_{k=1..n} (1/4)*(-1)^(k-1)*(56*k^2-32*k+5)/((2*k-1)^2 * binomial(3*k,k) * binomial(2*k,k) * k^3) ). - G. C. Greubel, Oct 08 2018 MAPLE a:=n->add((1/4)*(-1)^(k-1)*(56*k^2-32*k+5)/((2*k-1)^2*binomial(3*k, k)*binomial(2*k, k)*k^3), k=1..n): seq(denom(a(n)), n=1..10); # Muniru A Asiru, Oct 09 2018 MATHEMATICA Table[Denominator[Sum[(1/4)*(-1)^(k-1)*(56*k^2-32*k+5)/((2*k-1)^2*Binomial[3*k, k]* Binomial[2*k, k]*k^3), {k, 1, n}]], {n, 1, 30}] (* G. C. Greubel, Oct 08 2018 *) PROG (PARI) for(n=1, 15, print1(denominator(sum(k=1, n, (1/4)*(-1)^(k-1)*(56*k^2 -32*k +5)/((2*k-1)^2*binomial(3*k, k) *binomial(2*k, k)*k^3))), ", ")) (MAGMA) [Denominator((&+[(1/4)*(-1)^(k-1)*(56*k^2-32*k+5)/((2*k-1)^2*Binomial(3*k, k)*Binomial(2*k, k)*k^3): k in [1..n]])): n in [1..30]]; // G. C. Greubel, Oct 08 2018 (GAP) List(List([1..10], n->Sum([1..n], k->(1/4)*(-1)^(k-1)*(56*k^2-32*k+5)/((2*k-1)^2*Binomial(3*k, k)*Binomial(2*k, k)*k^3))), DenominatorRat); # Muniru A Asiru, Oct 09 2018 CROSSREFS Numerators are in A084223, decimal expansion is in A002117. Sequence in context: A229430 A054777 A301392 * A227257 A222999 A166788 Adjacent sequences:  A084221 A084222 A084223 * A084225 A084226 A084227 KEYWORD nonn,frac AUTHOR Ralf Stephan, May 19 2003 STATUS approved

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Last modified January 22 16:37 EST 2020. Contains 331152 sequences. (Running on oeis4.)