OFFSET
0,3
COMMENTS
Diagonal sums of number triangle A115253.
FORMULA
G.f.: c(x)c(x^2)/(1-x^3) where c(x) is the g.f. of A000108; a(n)=sum{k=0..floor(n/2), sum{j=0..n-k, [j<=k]*C(k-j)[j<=n-2k]*C(n-2k-j)}}.
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Paul Barry, Jan 18 2006
STATUS
approved