OFFSET
1,3
COMMENTS
REFERENCES
E. Barcucci, A. del Lungo and R. Pinzani, "Deco" polyominoes, permutations and random generation, Theoretical Computer Science, 159, 1996, 29-42.
FORMULA
The row generating polynomials are P(1,t)=t and P(n,t)=2t^n*product(2+t+t^2+...+t^j, j=1..n-2) for n>=2.
EXAMPLE
Triangle starts:
1;
0,2;
0,0,4,2;
0,0,0,8,8,6,2;
0,0,0,0,16,24,28,26,16,8,2;
MAPLE
for n from 1 to 8 do P[n]:=sort(expand(simplify(2*t^n*product(2+sum(t^i, i=1..j), j=1..n-2)))) od: for n from 1 to 8 do seq(coeff(P[n], t, j), j=1..n*(n-1)/2+1) od; # yields sequence in triangular form
CROSSREFS
KEYWORD
nonn,tabf
AUTHOR
Emeric Deutsch, Aug 08 2006
STATUS
approved