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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
OFFSET
1,1
COMMENTS
See A145375 for the numerators, references and a W. Lang link.
FORMULA
a(n) = denominator(r(n)), with the rationals (in lowest terms) r(n) := Sum_{k=1..n} (-1)^(k+1)/binomial(2*k,k).
EXAMPLE
Rationals r(n) (in lowest terms): [1/2, 1/3, 23/60, 31/84, 47/126, 1031/2772, 26827/72072, ...].
CROSSREFS
KEYWORD
nonn,frac,easy
AUTHOR
Wolfdieter Lang, Oct 17 2008, Nov 17 2008, Nov 25 2008
STATUS
approved