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

Author

Wolfdieter Lang, Jul 13 2007

Keywords

• nonn
• frac
• easy

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.

Crossrefs

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

Programs

PARI

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

Formula

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