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A145556 Denominators of partial sums of the alternating series of inverse central binomial coefficients. 3
2, 3, 60, 84, 126, 2772, 72072, 360360, 1225224, 23279256, 11639628, 503217, 13385572200, 2007835830, 465817912560, 2888071057872, 627841534320, 2489716429200, 534293145706320, 18423901576080, 4381203794791824, 941958815880242160, 261655226633400600 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

See A145375 for the numerators, references and a W. Lang link.

LINKS

Table of n, a(n) for n=1..23.

FORMULA

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

EXAMPLE

Rationals r(n) (in lowest terms): [1/2,1/3,23/60,31/84,47/126,1031/2772,26827/72072,...].

CROSSREFS

A145557/A145558.

Sequence in context: A299172 A154253 A097961 * A124083 A112098 A144545

Adjacent sequences:  A145553 A145554 A145555 * A145557 A145558 A145559

KEYWORD

nonn,frac,easy

AUTHOR

Wolfdieter Lang Oct 17 2008, Nov 17 2008, Nov 25 2008

STATUS

approved

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Last modified June 16 08:46 EDT 2021. Contains 345056 sequences. (Running on oeis4.)