OFFSET
0,4
COMMENTS
a(n)=Sum(k*A181299(n,k),k>=0).
REFERENCES
G. Castiglione, A. Frosini, E. Munarini, A. Restivo and S. Rinaldi, Combinatorial aspects of L-convex polyominoes, European Journal of Combinatorics, 28, 2007, 1724-1741.
LINKS
Index entries for linear recurrences with constant coefficients, signature (7,-12,-4,12,-4).
FORMULA
G.f. = z^2*(1-z)^3/[(1+z)(1-4z+2z^2)^2].
MAPLE
g := z^2*(1-z)^3/((1+z)*(1-4*z+2*z^2)^2): gser := series(g, z = 0, 30): seq(coeff(gser, z, n), n = 0 .. 27);
MATHEMATICA
LinearRecurrence[{7, -12, -4, 12, -4}, {0, 0, 1, 4, 19, 80}, 30] (* Harvey P. Dale, Apr 05 2023 *)
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Emeric Deutsch, Oct 12 2010
STATUS
approved