A130414 Denominators of partial sums for a series for Pi/3.

1, 18, 45, 1260, 945, 20790, 135135, 1081080, 765765, 87297210, 43648605, 4015671660, 5019589575, 30117537450, 436704293025, 216605329340400, 13537833083775, 27075666167550, 500899824099675, 2003599296398700

Offset

0,2

Comments

The numerators are given in A130413.

For the rationals r(n) see A130413 and the W. Lang link given there.

Links

Robert Israel, Table of n, a(n) for n = 0..1000

Formula

a(n) = denominator(r(n)), n>=0, with the rationals defined in A130413.

Maple

f:= n -> denom(1+ (4/3)*add(((-1)^(j+1))/((2*j+1)*((2*j+1)^2-1)), j=1..n)):
map(f, [$0..20]); # Robert Israel, Jul 27 2015

Crossrefs

Sequence in context: A179896 A075284 A057444 * A108642 A250784 A250731

Adjacent sequences: A130411 A130412 A130413 * A130415 A130416 A130417

Keyword

nonn,frac,easy

Author

Wolfdieter Lang, Jun 01 2007

Status

approved