OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = a(n-1) + 7*a(n-3) - 7*a(n-4) - 12*a(n-6) + 12*a(n-7) for n>9.
Empirical g.f.: 2*x*(26 - 3*x + 5*x^2 - 172*x^3 + 34*x^4 - 9*x^5 + 275*x^6 - 84*x^7 - 36*x^8) / ((1 - x)*(1 - 3*x^3)*(1 - 4*x^3)). - Colin Barker, Dec 05 2018
EXAMPLE
Some solutions for n=4:
..0..1..0..0....0..0..1..1....0..0..1..0....0..0..1..0....0..1..0..0
..2..2..0..2....2..2..0..0....0..2..2..0....0..2..2..0....1..1..2..1
..1..0..0..1....3..3..2..2....0..1..0..0....0..3..0..0....2..1..1..2
..0..1..0..0....1..1..3..3....0..0..1..0....0..0..3..0....0..1..0..0
..2..2..0..2....0..0..1..1....0..2..2..0....0..1..1..0....1..1..2..1
..3..0..0..1....2..2..0..2....0..1..0..0....0..2..0..0....2..1..1..2
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Dec 20 2014
STATUS
approved