OFFSET
1,3
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 3*a(n-1) - 3*a(n-2) + 3*a(n-3) - 3*a(n-4) + 3*a(n-5) - 2*a(n-6).
Empirical g.f.: x*(1 - 2*x + 2*x^2 - x^3 + x^4 - 2*x^5) / ((1 - x)*(1 - 2*x)*(1 - x + x^2)*(1 + x + x^2)). - Colin Barker, Jan 01 2019
EXAMPLE
All solutions for n=4:
..2..1....0..0....2..1....0..0....2..1
..0..0....2..1....0..0....0..0....2..1
..2..1....0..0....0..0....0..0....0..0
..0..0....0..0....2..1....0..0....2..1
..2..1....2..1....0..0....0..0....2..1
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Oct 16 2015
STATUS
approved