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Search: id:A145560
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| A145560 |
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Denominators of partial sums of a certain alternating series of inverse central binomial coefficients. |
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+0
2
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| 1, 12, 180, 5040, 8400, 831600, 75675600, 302702400, 15437822400, 293318625600, 248192683200, 74209612276800, 8388912692160, 964724959598400, 46628373047256000, 5781918257859744000, 10921401153735072000, 884633493452540832000, 621897345897136204896000
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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See A145559 for the numerators, references and a W. Lang link.
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FORMULA
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a(n)=(1/2)*denominator(r(n)), with the rationals (in lowest terms) r(n):=sum(((-1)^(k+1))/(binomial(2*k,k)*k^2),k=1..n).
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EXAMPLE
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Rationals r(n) (in lowest terms):[1/2, 11/24, 167/360, 4667/10080, 7781/16800, 770269/1663200, 70095379/151351200,...].
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CROSSREFS
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A145557/A145558.
Sequence in context: A051609 A001814 A013924 this_sequence A166773 A071990 A086948
Adjacent sequences: A145557 A145558 A145559 this_sequence A145561 A145562 A145563
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KEYWORD
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nonn,easy
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AUTHOR
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Wolfdieter Lang (wolfdieter.lang(AT)physik.uni-karlsruhe.de) Oct 13 2008
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