OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 14*a(n-1) - 57*a(n-2) + 56*a(n-3) - 16*a(n-4) for n>5.
Empirical g.f.: x*(6 - 48*x + 199*x^2 - 274*x^3 + 105*x^4) / (1 - 7*x + 4*x^2)^2. - Colin Barker, Sep 18 2018
EXAMPLE
Some solutions for n=4:
..0..1..0..2....0..1..0..2....0..1..2..1....0..1..0..1....0..1..0..2
..0..1..0..1....0..2..0..1....2..1..0..1....0..2..0..2....0..2..0..1
..0..2..0..1....0..1..0..2....2..1..0..2....1..2..1..0....0..1..2..1
..1..1..0..2....0..1..2..1....0..1..2..1....1..2..1..0....2..1..0..1
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Sep 25 2013
STATUS
approved