OFFSET
0,9
FORMULA
Column k has g.f. (x/(1+x))^k*sum{j=0..k, C(k,3j)x^(3j)}
EXAMPLE
Triangle begins
1,
0, 1,
0, -1, 1,
0, 1, -2, 1,
0, -1, 3, -3, 1,
0, 1, -4, 6, -4, 1,
0, -1, 5, -9, 10, -5, 1,
0, 1, -6, 12, -16, 15, -6, 1,
0, -1, 7, -15, 19, -25, 21, -7, 1,
0, 1, -8, 18, -16, 20, -36, 28, -8, 1,
0, -1, 9, -21, 4, 24, 6, -49, 36, -9, 1
CROSSREFS
KEYWORD
AUTHOR
Paul Barry, May 14 2006
STATUS
approved