OFFSET
1,1
COMMENTS
Column 4 of A218663.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 12*a(n-1) +45*a(n-2) +180*a(n-3) -27*a(n-4) -81*a(n-6).
Empirical g.f.: 9*x*(1 - x)*(1 + 14*x + 30*x^2 + 18*x^3 + 9*x^4) / ((1 + 3*x + 9*x^2 - 9*x^3)*(1 - 15*x - 9*x^2 - 9*x^3)). - Colin Barker, Mar 10 2018
EXAMPLE
Some solutions for n=3:
..0..1..0..1....1..0..1..0....0..0..0..0....1..0..0..0....1..1..1..1
..0..1..0..1....1..1..0..0....0..1..0..1....1..0..1..0....1..0..0..1
..0..0..0..1....0..0..0..1....0..1..1..1....0..1..1..1....0..1..1..0
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Nov 04 2012
STATUS
approved