OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = a(n-1) + 3*a(n-3) + a(n-4) for n>5.
Empirical g.f.: x*(18 + 11*x + 40*x^2 + 10*x^3 - 2*x^4) / (1 - x - 3*x^3 - x^4). - Colin Barker, Dec 26 2018
EXAMPLE
Some solutions for n=4:
..0..1..0....0..0..0....0..1..0....0..0..0....0..0..0....0..0..1....0..0..0
..0..1..0....0..0..0....0..1..0....0..0..0....0..1..0....0..0..0....0..0..1
..0..0..0....0..1..0....0..0..0....0..0..0....0..0..0....0..0..0....0..0..0
..0..0..0....0..0..0....0..0..0....1..0..0....0..0..0....0..0..0....0..0..0
..0..1..0....0..0..0....0..1..0....0..0..0....0..0..0....0..0..0....0..0..0
..0..1..0....0..0..1....1..0..0....0..0..0....1..0..0....0..1..0....0..0..0
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Jul 02 2015
STATUS
approved