A130548 Denominators of 6*(sum(1/binomial(2*k,k),k=1..n)-1/3), n>=1.

1, 1, 10, 70, 105, 2310, 5460, 20020, 340340, 6466460, 461890, 37182145, 106234700, 25160850, 55454513400, 1719089915400, 573029971800, 4011209802600, 148414762696200, 148414762696200, 196290492598200, 261655226633400600, 392482839950100900, 18446693477654742300, 64563427171791598050

Offset

1,3

Comments

Numerators are given by A130547.

For the rationals r(n):= 6*(sum(1/binomial(2*k,k),k=1..n)-1/3), n>=1, the Comtet reference and a W. Lang link see A130547.

Links

Table of n, a(n) for n=1..25.

Formula

a(n) = denominator(r(n)), n>=1.

Prog

(PARI) a(n) = denominator(6*(sum(k=1, n, 1/binomial(2*k, k)) - 1/3)); \\ Michel Marcus, Nov 09 2019

Crossrefs

Cf. A130547. (numerators).

Sequence in context: A016273 A128737 A320228 * A160662 A090084 A025221

Adjacent sequences: A130545 A130546 A130547 * A130549 A130550 A130551

Keyword

nonn,frac,easy

Author

Wolfdieter Lang, Jul 13 2007

Extensions

More terms from Michel Marcus, Nov 09 2019

Status

approved