OFFSET
1,3
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 2*a(n-1) + 4*a(n-2) - 3*a(n-3).
Conjectures from Colin Barker, Oct 26 2018: (Start)
G.f.: x*(1 - x) / ((1 - 3*x)*(1 + x - x^2)).
a(n) = (10*3^n + 2^(-n)*((-1+sqrt(5))^n*(-5+4*sqrt(5)) - (-1-sqrt(5))^n*(5+4*sqrt(5)))) / 55.
(End)
EXAMPLE
Some solutions for n=5:
..0..1....0..1....0..1....0..1....0..1....0..1....0..1....0..1....0..1....0..1
..0..1....0..1....0..1....0..1....0..1....0..1....0..1....0..1....0..1....0..1
..0..2....2..0....1..0....1..0....1..0....0..2....2..0....2..1....2..1....1..0
..0..2....2..0....1..0....1..0....1..0....0..2....2..0....2..1....2..0....1..0
..1..2....1..0....0..1....1..0....2..1....2..0....0..2....0..2....1..0....0..2
..1..2....1..0....0..1....1..0....2..1....2..0....0..2....0..2....1..0....0..2
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Mar 21 2014
STATUS
approved