OFFSET
1,1
COMMENTS
Column 7 of A190033.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..200
FORMULA
Empirical: a(n) = 2*a(n-1) -a(n-2) +a(n-3) -2*a(n-4) +a(n-5) +a(n-6) -a(n-7) for n>15.
Empirical g.f.: x*(1205 - 2055*x + 1001*x^2 - 1072*x^3 + 2143*x^4 - 1041*x^5 - 1254*x^6 + 798*x^7 + 77*x^8 - 4*x^9 - 28*x^10 - 60*x^11 - 68*x^12 + 289*x^14) / ((1 - x)*(1 - x - x^3 + x^4 - x^6)). - Colin Barker, May 03 2018
EXAMPLE
Some solutions for 4 X 9:
..0..0..0..0..0..0..0..1..0....0..0..0..0..0..0..0..0..1
..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
..1..0..0..0..0..0..0..0..0....1..0..0..0..0..0..0..0..0
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, May 04 2011
STATUS
approved