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
KEYWORD
nonn
AUTHOR
Benoit Cloitre, Mar 25 2004
STATUS
approved