OFFSET
1,1
COMMENTS
Column 2 of A218810.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 3*a(n-1) + 3*a(n-2) + 3*a(n-3) + a(n-4) + a(n-5) + a(n-6) + a(n-7).
Empirical g.f.: x*(1 + x)^2*(3 + x^4) / (1 - 3*x - 3*x^2 - 3*x^3 - x^4 - x^5 - x^6 - x^7). - Colin Barker, Jul 24 2018
EXAMPLE
Some solutions for n=3:
..1..0....0..1....1..0....0..0....1..1....0..1....1..0....0..1....0..1....0..1
..0..0....1..0....1..1....1..1....0..0....1..1....1..1....1..1....1..1....0..1
..1..0....0..0....0..1....0..1....1..0....0..0....1..0....1..1....0..1....1..1
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Nov 06 2012
STATUS
approved