OFFSET
0,2
REFERENCES
J. Labelle, Paths in the Cartesian, triangular and hexagonal lattices, Bulletin of the ICA, 17, 1996, 47-61.
LINKS
Index entries for linear recurrences with constant coefficients, signature (3,-2,1,-1).
FORMULA
G.f.: (1+z^2)(1+z+z^2)/[(1-z)(1-2z-z^3)]= 1+2*(2+z^2)/((z-1)*(z^2+2*z-1)).
a(n) = 2*a(n-1) + a(n-3) + 6 for n >= 4.
Conjecture: a(n) = A193641(n+2)-3, n>0 - R. J. Mathar, Jul 22 2022
MAPLE
g:=series((1+z^2)*(1+z+z^2)/(1-z)/(1-2*z-z^3), z=0, 35): 1, seq(coeff(g, z^n), n=1..34);
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Emeric Deutsch, Dec 07 2004
STATUS
approved