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Search: id:A145558
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| A145558 |
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Denominators of partial sums of a certain alternating series of inverse central binomial coefficients. |
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+0
6
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| 1, 6, 15, 420, 36, 1386, 36036, 40040, 6126120, 2116296, 255816, 267711444, 3346393050, 1745944200, 6850263420, 14440355289360, 1604483921040, 3800093497200, 2671465728531600, 534293145706320, 952435607563440, 941958815880242160, 362291852261631600
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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See A145557 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))/(k*binomial(2*k,k)),k=1..n).
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EXAMPLE
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Rationals r(n) (in lowest terms): [1/2, 5/12, 13/30, 361/840, 31/72, 1193/2772, 31021/72072,...].
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CROSSREFS
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A145375/A145556.
Sequence in context: A117062 A003155 A024081 this_sequence A145612 A068941 A107777
Adjacent sequences: A145555 A145556 A145557 this_sequence A145559 A145560 A145561
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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 17 2008
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EXTENSIONS
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%O line; changed offset from 0 to 1. - Wolfdieter Lang (wolfdieter.lang(AT)physik.uni-karlsruhe.de), Nov 17 2008
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