OFFSET
1,2
COMMENTS
Column 2 of A297959.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 2*a(n-1) - a(n-2) + 4*a(n-3) - 4*a(n-4) for n>5.
Empirical g.f.: (1 + x)*(1 + 2*x^2 - 4*x^3) / ((1 - x)*(1 - 2*x)*(1 + x + 2*x^2)). - Colin Barker, Feb 19 2018
EXAMPLE
Some solutions for n=7:
..0..1. .0..0. .0..0. .0..0. .0..1. .0..1. .0..1. .0..1. .0..1. .0..0
..1..0. .0..1. .1..1. .1..1. .1..0. .0..1. .1..0. .1..0. .0..1. .1..1
..0..1. .1..1. .0..0. .0..0. .1..0. .1..0. .1..0. .1..0. .0..1. .0..0
..1..0. .1..1. .1..0. .1..1. .1..0. .1..0. .0..1. .1..0. .0..1. .1..1
..0..1. .1..1. .1..1. .0..0. .0..1. .0..1. .1..0. .1..0. .0..1. .0..1
..0..1. .1..0. .0..0. .1..1. .1..0. .0..1. .0..1. .0..1. .1..0. .0..0
..0..1. .0..0. .1..1. .0..0. .1..0. .0..1. .1..0. .1..0. .1..0. .1..1
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Jan 09 2018
STATUS
approved