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%I #13 Jul 27 2015 22:05:52
%S 1,18,45,1260,945,20790,135135,1081080,765765,87297210,43648605,
%T 4015671660,5019589575,30117537450,436704293025,216605329340400,
%U 13537833083775,27075666167550,500899824099675,2003599296398700
%N Denominators of partial sums for a series for Pi/3.
%C The numerators are given in A130413.
%C For the rationals r(n) see A130413 and the W. Lang link given there.
%H Robert Israel, <a href="/A130414/b130414.txt">Table of n, a(n) for n = 0..1000</a>
%F a(n) = denominator(r(n)), n>=0, with the rationals defined in A130413.
%p f:= n -> denom(1+ (4/3)*add(((-1)^(j+1))/((2*j+1)*((2*j+1)^2-1)), j=1..n)):
%p map(f, [$0..20]);# _Robert Israel_, Jul 27 2015
%K nonn,frac,easy
%O 0,2
%A _Wolfdieter Lang_, Jun 01 2007
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