A107869 Column 1 of triangle A107867; a(n) = binomial( n*(n+1)/2 + n+1, n).

1, 3, 15, 120, 1365, 20349, 376740, 8347680, 215553195, 6358402050, 210980549208, 7778680504140, 315502265971620, 13961746143269400, 669413654240461560, 34569147570568156800, 1912924003884628655655, 112923282067713332728110

Offset: 0

Author

Paul D. Hanna, Jun 04 2005

Keywords

• nonn

Crossrefs

Cf. A107867, A107868.

Programs

PARI

a(n)=binomial(n*(n+1)/2+n+1,n)

Sage

[binomial(binomial(binomial(n+1,n),n-1),n-1) for n in range(1, 19)] # Zerinvary Lajos, Nov 30 2009