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

Offset: 0

Author

Clark Kimberling

Keywords

• nonn

Programs

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

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~

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

Extensions

Corrected offset, more terms, Joerg Arndt, May 13 2013