OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 12*a(n-1) - 23*a(n-2) + 37*a(n-3) - 33*a(n-4).
Empirical g.f.: 4*x*(41 - 79*x + 134*x^2 - 132*x^3) / (1 - 12*x + 23*x^2 - 37*x^3 + 33*x^4). - Colin Barker, Nov 23 2018
EXAMPLE
Some solutions for n=4:
..3..2....1..2....2..0....0..2....1..0....0..0....3..2....0..0....3..2....3..1
..0..1....0..3....1..1....1..3....1..3....1..1....2..1....3..3....0..1....2..0
..1..1....2..3....3..3....3..3....3..2....1..3....1..2....2..0....1..1....1..0
..2..2....2..3....1..0....3..0....3..1....1..3....1..2....1..1....0..2....0..0
..2..0....3..3....1..3....2..0....1..3....2..2....2..0....2..2....3..2....2..2
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Nov 28 2014
STATUS
approved