OFFSET
0,2
COMMENTS
FORMULA
G.f.: (1+2x)(1+2x*y)/((1-x)(1-x*y)(1-x^2*y)); Number triangle T(n, k)=sum{j=0..n, [j<=k]*(3-2*0^(k-j))*[j<=n-k]*(3-2*0^(n-k-j))}.
EXAMPLE
Triangle begins
1;
3, 3;
3,10, 3;
3,12,12, 3;
3,12,19,12, 3;
3,12,21,21,12, 3;
3,12,21,28,21,12,3;
CROSSREFS
KEYWORD
AUTHOR
Paul Barry, Jan 19 2006
STATUS
approved