A145560 Denominators of partial sums of a certain alternating series of inverse central binomial coefficients.

1, 12, 180, 5040, 8400, 831600, 75675600, 302702400, 15437822400, 293318625600, 248192683200, 74209612276800, 8388912692160, 964724959598400, 46628373047256000, 5781918257859744000, 10921401153735072000, 884633493452540832000, 621897345897136204896000

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: A370750 A327079 A013924 * A332960 A230345 A166773

Adjacent sequences: A145557 A145558 A145559 * A145561 A145562 A145563

Keyword

nonn,frac,easy

Author

Wolfdieter Lang, Oct 13 2008

Status

approved