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%I #6 Jul 02 2023 14:25:09
%S 1,6,15,420,36,1386,36036,40040,6126120,2116296,255816,267711444,
%T 3346393050,1745944200,6850263420,14440355289360,1604483921040,
%U 3800093497200,2671465728531600,534293145706320,952435607563440,941958815880242160,362291852261631600
%N Denominators of partial sums of a certain alternating series of inverse central binomial coefficients.
%C See A145557 for the numerators, references and a W. Lang link.
%F a(n)=(1/2)*denominator(r(n)), with the rationals (in lowest terms) r(n):=sum(((-1)^(k+1))/(k*binomial(2*k,k)),k=1..n).
%e Rationals r(n) (in lowest terms): [1/2, 5/12, 13/30, 361/840, 31/72, 1193/2772, 31021/72072,...].
%Y Cf. A145375/A145556, A145557.
%K nonn,frac,easy
%O 1,2
%A _Wolfdieter Lang_, Oct 17 2008
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