A120995 Denominators of rationals related to John Wallis' product formula for Pi/2 (from his 'Arithmetica infinitorum' from 1659).

1, 15, 175, 3675, 14553, 231231, 920205, 234652275, 2807136475, 14933966047, 59612442981, 11425718238025, 15211755050625, 243077636829375, 971230202264925, 993568496917018275, 3970836034391543625

Offset

1,2

Comments

The corresponding numerators are A120994.

The rationals W(n):= (((4^n)/binomial(2*n,n))^2)/(2*n+1) converge to Pi/2 = 1.570796327...

Links

Table of n, a(n) for n=1..17.

Formula

a(n) = denominators((3/4)*W(n)), n>=1.

Crossrefs

Sequence in context: A145147 A069379 A184285 * A024197 A210782 A071535

Adjacent sequences: A120992 A120993 A120994 * A120996 A120997 A120998

Keyword

nonn,easy,frac

Author

Wolfdieter Lang, Aug 01 2006

Status

approved