OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 5*a(n-1) - 25*a(n-3) + 25*a(n-4) for n>5.
Empirical g.f.: 4*x*(52 - 91*x - 234*x^2 + 454*x^3 - 130*x^4) / ((1 - 5*x + 5*x^2)*(1 - 5*x^2)). - Colin Barker, Dec 18 2018
EXAMPLE
Some solutions for n=4:
..1..1..1....1..1..1....1..1..0....1..1..1....0..0..0....1..0..0....0..1..1
..1..0..1....1..1..1....1..1..0....1..1..1....0..1..1....0..1..1....1..1..1
..1..1..1....1..1..0....1..1..1....1..1..0....1..1..1....1..1..1....0..1..1
..1..1..0....1..1..0....1..1..0....1..1..1....1..1..1....1..1..1....0..1..1
..1..1..0....1..0..0....1..1..1....1..0..1....0..1..0....1..1..0....1..1..1
..1..0..0....0..1..1....1..1..1....1..0..1....0..1..0....0..0..0....1..1..1
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Feb 14 2015
STATUS
approved