OFFSET

1,2

COMMENTS

Column 2 of A221573

LINKS

R. H. Hardin, Table of n, a(n) for n = 1..210

FORMULA

Empirical: a(n) = 3*a(n-1) -2*a(n-2) +4*a(n-4).

Empirical g.f.: -x^2*(5-6*x+8*x^2) / ( -1+3*x-2*x^2+4*x^4 ). - R. J. Mathar, Jun 06 2013

EXAMPLE

Some solutions for n=6

..2....1....2....0....0....1....2....0....0....0....0....2....0....2....0....1

..0....1....2....0....0....1....0....2....2....0....0....0....0....2....0....1

..0....1....1....2....2....0....0....2....2....2....2....1....2....1....0....2

..0....0....1....2....0....0....0....0....0....0....2....1....2....1....2....2

..2....0....2....2....2....1....1....2....0....0....1....2....2....2....0....0

..0....0....2....2....2....1....1....2....2....2....1....0....0....0....0....2

CROSSREFS

KEYWORD

nonn

AUTHOR

R. H. Hardin Jan 20 2013

STATUS

approved