OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 10*a(n-1) - 29*a(n-2) + 20*a(n-3) - 4*a(n-4) for n>5.
Empirical g.f.: 2*x*(1 - 6*x + 18*x^2 - 16*x^3 + 4*x^4) / (1 - 5*x + 2*x^2)^2. - Colin Barker, Sep 18 2018
EXAMPLE
Some solutions for n=4:
..0..1..2....0..1..2....0..1..0....0..1..0....0..1..0....0..1..2....0..1..2
..0..1..2....0..2..0....0..1..0....1..2..0....0..1..0....0..2..0....2..0..2
..2..1..2....0..2..1....0..1..0....0..2..1....1..2..0....0..2..0....1..0..1
..1..0..2....1..2..0....0..2..2....1..2..1....0..2..0....0..2..1....2..0..1
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Sep 25 2013
STATUS
approved