OFFSET
1,2
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 2*a(n-1) + 7*a(n-2) - 24*a(n-4) - 32*a(n-5) - 16*a(n-6) for n>8.
Empirical g.f.: 4*x^2*(1 - 4*x^2 - 8*x^3 - 2*x^4 + 8*x^5 + 8*x^6) / (1 - x - 4*x^2 - 4*x^3)^2. - Colin Barker, Feb 12 2019
EXAMPLE
Some solutions for n=4:
..0..1. .0..0. .0..0. .0..0. .0..0. .0..0. .0..0. .0..0. .0..0. .0..0
..1..1. .1..0. .0..0. .0..1. .0..1. .0..1. .0..1. .0..1. .0..0. .1..1
..1..0. .0..0. .0..0. .2..2. .1..1. .1..1. .0..0. .1..1. .0..0. .1..1
..0..0. .0..0. .0..1. .2..2. .1..0. .2..1. .0..0. .1..2. .1..1. .1..1
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Dec 26 2016
STATUS
approved