OFFSET
1,2
COMMENTS
Column 1 of A210095.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 10*a(n-1) - 27*a(n-2) + 10*a(n-3) + 8*a(n-4).
Empirical g.f.: 9*x^2 / ((1 - x)*(1 - 4*x)*(1 - 5*x - 2*x^2)). - Colin Barker, Jul 14 2018
EXAMPLE
Some solutions for n=4:
..0..0....0..0....0..1....0..0....0..1....0..0....0..0....0..1....0..0....0..1
..1..0....0..0....0..0....1..1....1..1....0..1....0..1....1..1....0..1....0..1
..1..0....0..0....1..0....1..0....0..0....0..0....0..0....1..0....0..0....0..0
..0..0....1..1....0..0....1..1....1..1....0..2....2..0....1..1....0..2....2..0
..0..2....1..2....0..2....1..2....1..2....2..0....0..0....2..1....0..2....2..2
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Mar 17 2012
STATUS
approved