OFFSET
0,2
COMMENTS
LINKS
G. Castiglione, A. Frosini, E. Munarini, A. Restivo, and S. Rinaldi, Combinatorial aspects of L-convex polyominoes, European J. Combin. 28 (2007), no. 6, 1724-1741.
FORMULA
G.f.: G(t,z) = (1+z)*(1-z)^2/(1-3*z-z^2+z^3-t*(1-z)*z^2).
EXAMPLE
T(3,1)=4 because we have (1,1/1,0),(1,0/1,1),(1,1/0,1),(0,1/1,1) (the 2-compositions are written as (top row/bottom row).
Triangle starts:
1;
2;
6,1;
20,4;
64,17,1;
MAPLE
G := (1-z)^2*(1+z)/(1-3*z-z^2+z^3-t*z^2*(1-z)): Gser := simplify(series(G, z = 0, 15)): for n from 0 to 13 do P[n] := sort(coeff(Gser, z, n)) end do: for n from 0 to 13 do seq(coeff(P[n], t, k), k = 0 .. floor((1/2)*n)) end do; # yields sequence in triangular form
CROSSREFS
KEYWORD
nonn,tabf
AUTHOR
Emeric Deutsch, Oct 12 2010
STATUS
approved