OFFSET
1,1
COMMENTS
Column 2 of A186881.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..200
FORMULA
Empirical: a(n) = 2*a(n-1) - a(n-2) + 3*a(n-3) - 6*a(n-4) + 3*a(n-5) + 3*a(n-6) - 3*a(n-7) for n>10.
Empirical g.f.: x*(2428 - 4435*x + 2787*x^2 - 2436*x^3 + 15069*x^4 - 11457*x^5 - 22980*x^6 + 1305*x^7 + 12492*x^8 + 7047*x^9) / ((1 - x)*(1 - x - 3*x^3 + 3*x^4 - 3*x^6)). - Colin Barker, Apr 19 2018
EXAMPLE
Some solutions for 6 X 4:
..0..0..2..0....1..0..0..0....0..0..3..0....1..0..0..0....1..1..1..1
..0..0..0..0....0..0..0..0....0..0..0..1....0..0..0..3....0..0..0..0
..0..0..0..0....0..0..0..0....0..0..0..0....0..0..0..0....0..0..0..0
..0..0..0..0....0..0..0..0....0..0..0..0....0..0..0..0....0..0..0..0
..3..0..0..0....3..0..0..0....2..0..0..0....0..0..0..0....3..0..0..0
..2..3..0..0....0..2..0..0....2..2..0..0....0..0..0..3....3..1..0..0
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Feb 28 2011
STATUS
approved