A026616 T(2n,n), T given by A026615.

1, 3, 10, 34, 120, 434, 1596, 5940, 22308, 84370, 320892, 1226108, 4702880, 18097044, 69832600, 270118440, 1047043260, 4066132050, 15816664380, 61615392300, 240347793840, 938669220060, 3669940053000

Offset

0,2

Comments

If Y is a fixed 3-subset of a (2n+1)-set X then a(n) is the number of (n+1)-subsets of X intersecting Y. - Milan Janjic, Oct 28 2007

Links

Table of n, a(n) for n=0..22.

Milan Janjic, Two Enumerative Functions

Formula

a(n) = (1/2)*((7*n-4)/(2*n-1))*binomial(2*n, n), n>0. G.f.: (2-x)/sqrt(1-4*x)-1. - Vladeta Jovovic, Jan 08 2004

Crossrefs

Sequence in context: A178578 A188622 A047017 * A306409 A047032 A362389

Adjacent sequences: A026613 A026614 A026615 * A026617 A026618 A026619

Keyword

nonn

Author

Clark Kimberling

Status

approved