OFFSET
1,3
COMMENTS
Column 2 of A297978.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = a(n-1) + 3*a(n-2) + 2*a(n-3).
Empirical g.f.: x^2*(1 + 2*x) / (1 - x - 3*x^2 - 2*x^3). - Colin Barker, Feb 19 2018
EXAMPLE
Some solutions for n=7:
..0..0. .0..0. .0..0. .0..0. .0..0. .0..0. .0..0. .0..0. .0..0. .0..0
..0..0. .0..0. .0..0. .1..0. .0..1. .0..0. .0..0. .0..0. .0..0. .0..0
..1..1. .0..0. .0..0. .1..1. .1..1. .1..1. .1..0. .0..0. .0..0. .1..1
..1..0. .0..0. .0..1. .0..0. .1..0. .1..1. .1..1. .1..0. .0..1. .1..1
..0..0. .1..0. .1..1. .0..0. .0..0. .1..1. .1..1. .1..1. .1..1. .1..0
..1..1. .1..1. .0..0. .1..0. .1..0. .1..1. .1..0. .0..0. .1..0. .0..0
..1..1. .1..1. .0..0. .1..1. .1..1. .1..1. .0..0. .0..0. .0..0. .0..0
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Jan 10 2018
STATUS
approved