A092473 a(n) = Sum_{i+j+k=n, 0<=i<=j<=k<=n} (2n)!/((i+j)! * (j+k)! * (k+i)!).

1, 2, 18, 170, 1330, 11382, 117810, 934362, 8611746, 82240730, 699393838, 6244164940, 59910383026, 507902083210, 4599466921410, 43063170064620, 372282144948450, 3338235118237410, 31231394376541650, 270058012725600000

Offset

0,2

Links

Vaclav Kotesovec, Table of n, a(n) for n = 0..1000 (terms 0..200 from Seiichi Manyama)

Vaclav Kotesovec, Plot a(n+1)/a(n) for n = 1..999

Prog

(PARI) a(n)=sum(i=0, n, sum(j=0, i, sum(k=0, j, if(i+j+k-n, 0, (2*n)!/(i+j)!/(j+k)!/(k+i)!))))

Crossrefs

Cf. A092472.

Sequence in context: A052665 A259880 A364524 * A318218 A073558 A132306

Adjacent sequences: A092470 A092471 A092472 * A092474 A092475 A092476

Keyword

nonn

Author

Benoit Cloitre, Mar 25 2004

Status

approved