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A145560 Denominators of partial sums of a certain alternating series of inverse central binomial coefficients. 2
1, 12, 180, 5040, 8400, 831600, 75675600, 302702400, 15437822400, 293318625600, 248192683200, 74209612276800, 8388912692160, 964724959598400, 46628373047256000, 5781918257859744000, 10921401153735072000, 884633493452540832000, 621897345897136204896000 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

See A145559 for the numerators, references and a W. Lang link.

LINKS

Robert Israel, Table of n, a(n) for n = 1..772

FORMULA

a(n) = (1/2)*denominator(r(n)), with the rationals (in lowest terms) r(n) := Sum_{k=1..n} (-1)^(k+1)/(binomial(2*k,k)*k^2).

EXAMPLE

Rationals r(n) (in lowest terms): [1/2, 11/24, 167/360, 4667/10080, 7781/16800, 770269/1663200, 70095379/151351200,...].

MAPLE

map(denom, ListTools:-PartialSums([seq(2*(-1)^(k+1)/(binomial(2*k, k)*k^2), k=1..30)])): # Robert Israel, Sep 24 2017

CROSSREFS

Cf. A145557/A145558, A145559.

Sequence in context: A001814 A327079 A013924 * A230345 A166773 A202632

Adjacent sequences:  A145557 A145558 A145559 * A145561 A145562 A145563

KEYWORD

nonn,easy

AUTHOR

Wolfdieter Lang Oct 13 2008

STATUS

approved

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Last modified January 27 17:58 EST 2020. Contains 331296 sequences. (Running on oeis4.)