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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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5
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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; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| See A145557 for the numerators, references and a W. Lang link.
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FORMULA
| 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
| 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
| A145375/A145556.
Sequence in context: A003155 A199095 A024081 * A145612 A191463 A068941
Adjacent sequences: A145555 A145556 A145557 * A145559 A145560 A145561
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KEYWORD
| nonn,easy
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AUTHOR
| Wolfdieter Lang (wolfdieter.lang(AT)physik.uni-karlsruhe.de) Oct 17 2008
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