OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = a(n-1) + 4*a(n-2) - 2*a(n-3) - 4*a(n-4).
Conjectures from Colin Barker, Jul 18 2018: (Start)
G.f.: x*(7 + 10*x - 8*x^2 - 12*x^3) / ((1 + x)*(1 - 2*x)*(1 - 2*x^2)).
a(n) = (-9*2^(n/2) + 17*2^n + 1)/3 for n even.
a(n) = (17*2^n - 3*2^((n+3)/2) - 1)/3 for n odd.
(End)
EXAMPLE
Some solutions for n=5:
..0....0....0...-1....0....1....1....0....0....1....0....0....1...-1....0....1
..0....1....0....1....0...-1....0...-1....1...-1....1....0....0....0....1....0
.-1....0...-1....0....0....1....0....0...-1....0...-1....0...-1....0....0....0
..0....0....0...-1...-1...-1....0...-1....0...-1....1....1....0....1...-1....0
..1....0....0....0....0....1...-1....0....1....1....0....0...-1....0....1....1
..0...-1....1...-1...-1....0....0....0...-1...-1....1....1....1....1....0....0
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Apr 12 2012
STATUS
approved