OFFSET
1,2
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 24*a(n-1) - 204*a(n-2) + 704*a(n-3) - 816*a(n-4) + 384*a(n-5) - 64*a(n-6) for n>7.
Empirical g.f.: x*(1 - 21*x + 156*x^2 - 436*x^3 + 264*x^4 - 192*x^5 + 32*x^6) / (1 - 8*x + 4*x^2)^3. - Colin Barker, Feb 11 2019
EXAMPLE
Some solutions for n=4:
..0..0. .0..0. .0..0. .0..1. .0..1. .0..1. .0..1. .0..1. .0..0. .0..0
..0..1. .0..1. .1..2. .1..1. .1..0. .2..2. .1..2. .1..0. .0..1. .1..1
..2..1. .0..1. .1..1. .1..0. .0..0. .2..2. .2..2. .0..0. .0..2. .1..2
..0..1. .2..0. .1..2. .1..2. .2..2. .1..2. .2..0. .1..1. .2..0. .0..2
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Dec 16 2016
STATUS
approved