A027909 - OEIS

A027909

T(2n,n-1), T given by A027907.

1, 4, 21, 112, 615, 3432, 19383, 110448, 633726, 3656360, 21191555, 123286440, 719539015, 4210967880, 24702429825, 145210795200, 855172338570, 5044470461352, 29799593861974, 176268499363840, 1043889366927771, 6188748520285584, 36726461258947569, 218146172715259488, 1296812014083995850

(list; graph; refs; listen; history; text; internal format)

OFFSET

0,2

LINKS

Table of n, a(n) for n=0..24.

FORMULA

G.f.: -g*(g^2+g+1)/(3*g^2+g-1) where g = x times the g.f. of A143927. - Mark van Hoeij, Nov 16 2011

MAPLE

seq(add(binomial(j, 2*j-3*n-4)*binomial(2*n+2, j), j=0...2*n+2), n=0..25); # Mark van Hoeij, May 12 2013

PROG

(PARI) a(n)=sum(j=0, 2*n+2, binomial(j, 2*j-3*n-4)*binomial(2*n+2, j)); \\ Joerg Arndt, May 13 2013~

CROSSREFS