OFFSET
0,5
FORMULA
Number triangle T(n,k)=sum{j=0..n, C(k,k-j)*C(n-j,k)*C(2,j)}*[k<=n]
EXAMPLE
Triangle begins
1,
1, 1,
1, 4, 1,
1, 7, 7, 1,
1, 10, 19, 10, 1,
1, 13, 37, 37, 13, 1,
1, 16, 61, 92, 61, 16, 1,
1, 19, 91, 185, 185, 91, 19, 1
CROSSREFS
KEYWORD
AUTHOR
Paul Barry, Oct 28 2006
STATUS
approved