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A130414
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Denominators of partial sums for a series for Pi/3.
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2
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1, 18, 45, 1260, 945, 20790, 135135, 1081080, 765765, 87297210, 43648605, 4015671660, 5019589575, 30117537450, 436704293025, 216605329340400, 13537833083775, 27075666167550, 500899824099675, 2003599296398700
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OFFSET
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0,2
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COMMENTS
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The numerators are given in A130413.
For the rationals r(n) see A130413 and the W. Lang link given there.
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LINKS
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Robert Israel, Table of n, a(n) for n = 0..1000
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FORMULA
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a(n) = denominator(r(n)), n>=0, with the rationals defined in A130413.
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MAPLE
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f:= n -> denom(1+ (4/3)*add(((-1)^(j+1))/((2*j+1)*((2*j+1)^2-1)), j=1..n)):
map(f, [$0..20]); # Robert Israel, Jul 27 2015
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CROSSREFS
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Sequence in context: A179896 A075284 A057444 * A108642 A250784 A250731
Adjacent sequences: A130411 A130412 A130413 * A130415 A130416 A130417
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KEYWORD
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nonn,frac,easy
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AUTHOR
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Wolfdieter Lang, Jun 01 2007
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STATUS
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approved
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