OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 4*a(n-1) - 2*a(n-2) - 9*a(n-4) - 4*a(n-5) - 4*a(n-6) for n>9.
Empirical g.f.: x*(2 + 2*x + 13*x^2 - 8*x^3 + x^4 - 36*x^5 + 12*x^6 + 16*x^8) / (1 - 2*x - x^2 - 2*x^3)^2. - Colin Barker, Feb 11 2019
EXAMPLE
Some solutions for n=4:
..0..0..0. .0..0..0. .0..1..1. .0..1..1. .0..0..0. .0..1..1. .0..0..1
..1..1..1. .1..1..1. .1..1..1. .0..1..1. .0..0..0. .0..1..1. .1..1..1
..1..1..1. .1..1..1. .1..1..1. .0..1..1. .1..0..0. .0..0..0. .1..1..1
..2..2..1. .1..0..1. .0..0..0. .0..0..1. .1..0..0. .0..2..0. .2..2..2
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Dec 20 2016
STATUS
approved