OFFSET
1,1
COMMENTS
Column 2 of A209503.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 16*a(n-1) - 10*a(n-2) - 168*a(n-3) - 72*a(n-4) for n>5.
Empirical g.f.: x*(2 - 26*x - 19*x^2 + 174*x^3 + 75*x^4) / ((1 - 4*x - 2*x^2)*(1 - 12*x - 36*x^2)). - Colin Barker, Jul 10 2018
EXAMPLE
Some solutions for n=4.
..0..0....0..0....0..1....0..0....0..0....0..0....0..0....0..0....0..1....0..0
..1..2....1..2....0..2....1..2....1..2....1..2....1..2....1..2....1..2....1..2
..3..1....2..0....1..0....0..1....2..3....0..2....1..0....0..1....0..2....2..3
..2..1....0..3....2..0....0..2....2..1....3..2....2..0....2..1....1..0....4..2
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Mar 09 2012
STATUS
approved