OFFSET
1,2
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 5*a(n-1) - 4*a(n-2) - 14*a(n-3) + 19*a(n-4) + 13*a(n-5) - 22*a(n-6) - 4*a(n-7) + 8*a(n-8) for n>9.
Empirical g.f.: x*(1 - x + 17*x^2 - 39*x^3 - 56*x^4 + 92*x^5 + 94*x^6 - 44*x^7 - 80*x^8) / ((1 - x)^2*(1 + x)^3*(1 - 2*x)^3). - Colin Barker, Feb 12 2019
EXAMPLE
Some solutions for n=4:
..0..0. .0..0. .0..0. .0..0. .0..1. .0..0. .0..0. .0..1. .0..0. .0..1
..0..0. .1..0. .1..0. .0..0. .1..1. .0..1. .1..1. .0..1. .1..1. .2..2
..1..2. .1..1. .2..0. .0..1. .1..0. .0..1. .1..0. .0..0. .1..1. .2..2
..1..1. .1..1. .0..0. .1..1. .1..1. .0..0. .1..0. .2..2. .0..2. .0..0
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Dec 21 2016
STATUS
approved