OFFSET
1,1
COMMENTS
Column 1 of A206521.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 18*a(n-1) - 27*a(n-2) - 76*a(n-3) - 111*a(n-4) - 66*a(n-5) - 24*a(n-6) for n>7.
Empirical g.f.: x*(15 - 84*x - 157*x^2 - 182*x^3 - 80*x^4 - 18*x^5 + 8*x^6) / ((1 - 3*x - 3*x^2 - 2*x^3)*(1 - 15*x - 15*x^2 - 12*x^3)). - Colin Barker, Jun 17 2018
EXAMPLE
Some solutions for n=4:
..0..1....0..0....0..1....0..0....0..0....0..0....0..0....0..0....0..1....0..0
..1..0....0..0....1..0....1..0....0..1....0..1....0..0....0..0....2..2....1..0
..2..1....0..1....0..0....0..1....1..2....2..0....1..1....1..2....1..0....0..1
..1..1....0..1....0..1....1..0....0..1....0..1....2..0....1..3....0..3....1..0
..0..3....1..2....0..0....0..0....0..0....3..0....2..2....0..0....0..0....0..1
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Feb 08 2012
STATUS
approved