OFFSET
1,4
COMMENTS
Column 1 of A198669.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..200
FORMULA
Empirical: a(n) = 4*a(n-1) + a(n-2) - 17*a(n-3) + 6*a(n-4) + 21*a(n-5) - 6*a(n-6) - 8*a(n-7) for n>8.
Empirical g.f.: x^2*(1 - 3*x^2 - x^3)*(1 - 3*x + 3*x^3) / ((1 - x)*(1 + x)*(1 - 2*x)*(1 - x - x^2)*(1 - x - 4*x^2)). - Colin Barker, Mar 02 2018
EXAMPLE
All solutions for n=5:
..0....0....0
..0....0....0
..1....0....0
..1....0....1
..1....0....1
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Oct 28 2011
STATUS
approved