OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..69
FORMULA
Empirical: a(n) = 3*a(n-1) - 6*a(n-3) + 4*a(n-4).
Conjectures from Colin Barker, Jul 18 2018: (Start)
G.f.: 2*x*(4 - 3*x - 11*x^2 + 6*x^3) / ((1 - x)*(1 - 2*x)*(1 - 2*x^2)).
a(n) = 9*2^(n/2) + 2^(n+1) - 8 for n even.
a(n) = 2*(2^n + 3*2^((n+1)/2) - 4) for n odd.
(End)
EXAMPLE
Some solutions for n=5:
.-1...-1...-1....0....0...-1....1....0...-1....1....1....1...-1...-1....1....0
..0....1...-1....1...-1....1....1....1....1...-1....1....1....1...-1...-1....1
.-1....0...-1....0....0....1...-1....0....0...-1...-1....1...-1....1....1...-1
..0....1...-1...-1....1...-1...-1....1....1....1...-1....1....0...-1....1....1
..1....0....1....0....0....1....1....0...-1...-1...-1....1...-1....1....1....0
..0....1....1....1...-1....1...-1....1....1...-1....1....1....1...-1....1....1
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Apr 14 2012
STATUS
approved