OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 18*a(n-1) - 111*a(n-2) + 282*a(n-3) - 333*a(n-4) + 180*a(n-5) - 36*a(n-6) for n>7.
Empirical g.f.: 6*x*(10 - 69*x + 162*x^2 - 157*x^3 + 87*x^4 - 36*x^5 + 8*x^6) / (1 - 9*x + 15*x^2 - 6*x^3)^2.- Colin Barker, Jan 14 2019
EXAMPLE
Some solutions for n=4:
..1..2..2..2. .2..0..1..2. .2..2..2..2. .0..0..1..2. .2..1..0..1
..0..1..2..1. .2..1..2..2. .1..2..2..2. .0..1..2..2. .2..2..1..0
..1..2..1..0. .1..2..1..2. .2..2..2..2. .1..2..2..2. .2..1..0..1
..0..1..0..1. .2..1..0..1. .1..1..2..1. .0..2..2..2. .1..2..1..2
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Feb 09 2016
STATUS
approved