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A130546
Denominators of 2*Sum_{k=1..n} 1/binomial(2*k,k), n >= 1.
1
1, 3, 30, 210, 315, 6930, 16380, 60060, 1021020, 19399380, 461890, 37182145, 106234700, 75482550, 166363540200, 5157269746200, 1719089915400, 12033629407800, 445244288088600, 445244288088600, 588871477794600, 784965679900201800, 1177448519850302700, 55340080432964226900
OFFSET
1,2
COMMENTS
Numerators are given by A130545.
For the rationals r(n) := 2*Sum_{k=1..n} 1/binomial(2*k,k), n >= 1, the Comtet reference and a W. Lang link see A130545.
FORMULA
a(n) = denominator(r(n)), n >= 1.
MATHEMATICA
Accumulate[Table[2 1/Binomial[2n, n], {n, 30}]]//Denominator (* Harvey P. Dale, Aug 12 2022 *)
PROG
(PARI) a(n) = denominator(2*sum(k=1, n, 1/binomial(2*k, k))); \\ Michel Marcus, Nov 09 2019
CROSSREFS
Cf. A130545 (numerators).
Sequence in context: A003771 A121100 A203366 * A051133 A332426 A043030
KEYWORD
nonn,frac,easy
AUTHOR
Wolfdieter Lang, Jul 13 2007
EXTENSIONS
More terms from Michel Marcus, Nov 09 2019
STATUS
approved