A145565 Denominators of partial sums of a certain series of inverse central binomial coefficients.

1, 4, 36, 720, 25200, 10800, 5821200, 302702400, 908107200, 15437822400, 3226504881600, 248192683200, 964724959598400, 964724959598400, 1607874932664000, 186513492189024000, 98292610383615648000, 1605505432763232000, 16808036375598275808000, 124379469179427240979200

Offset

0,2

Comments

See A145564 for the numerators, a reference and a W. Lang link.

Links

Table of n, a(n) for n=0..19.

Formula

a(n)=denominator(r(n)), with the rationals (in lowest terms) r(n):=sum(1/(binomial(2*k,k)*(k+1)),k=0..n).

Example

Rationals r(n) (in lowest terms):[1, 5/4, 47/36, 949/720, 33287/25200, 14273/10800, 7694047/5821200,...].

Crossrefs

Cf. A145564.

Sequence in context: A156630 A289545 A322782 * A360903 A214669 A126152

Adjacent sequences: A145562 A145563 A145564 * A145566 A145567 A145568

Keyword

nonn,frac,easy

Author

Wolfdieter Lang, Oct 17 2008

Status

approved