A130554 Denominators of partial sums for a series for 2*Pi*sqrt(3)/9.

1, 6, 5, 140, 1260, 110, 60060, 72072, 680680, 12932920, 38798760, 11440660, 185910725, 5736673800, 4621209450, 3438179830800, 10314539492400, 140744203600, 59365905078480, 127212653739600, 4056670180362800

Offset

1,2

Comments

Numerators are given in A130553.

For the rationals r(n) := 2*Sum_{j=1..n} 1/(j*binomial(2*j,j)), n >= 1, the A. Comtet reference and a W. Lang link see A130553.

Links

Table of n, a(n) for n=1..21.

Formula

a(n) = denominator(r(n)), n >= 1, with the rationals r(n) defined above.

Prog

(PARI) a(n) = denominator(2*sum(j=1, n, 1/(j*binomial(2*j, j)))); \\ Michel Marcus, Nov 09 2019

Crossrefs

Cf. A130553 (numerators), A248897 (2*Pi*sqrt(3)/9).

Sequence in context: A223529 A189422 A266980 * A291067 A037054 A284740

Adjacent sequences: A130551 A130552 A130553 * A130555 A130556 A130557

Keyword

nonn,frac,easy

Author

Wolfdieter Lang, Jul 13 2007

Status

approved