OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 5*a(n-1) - 2*a(n-2) - 4*a(n-3) for n>5.
Empirical g.f.: x*(1 - x - x^2)*(2 - x - 2*x^2) / (1 - 5*x + 2*x^2 + 4*x^3). - Colin Barker, Oct 30 2018
EXAMPLE
Some solutions for n=4:
..0..1..0..0....0..1..2..0....0..1..0..1....0..1..1..0....0..1..0..2
..1..2..0..0....1..0..2..0....0..1..2..1....0..1..1..0....1..0..2..1
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Apr 20 2014
STATUS
approved