OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = a(n-2) + 2*a(n-3) + 4*a(n-4) + 3*a(n-6) - 8*a(n-7) + 9*a(n-8) - 6*a(n-9) - 4*a(n-10) - 4*a(n-11) - 4*a(n-12) for n>13.
Empirical g.f.: x*(36 + 50*x + 60*x^2 + 44*x^3 - 33*x^4 - 18*x^5 - 116*x^6 + 106*x^7 - 231*x^8 - 78*x^9 - 72*x^10 - 36*x^11 + 28*x^12) / (1 - x^2 - 2*x^3 - 4*x^4 - 3*x^6 + 8*x^7 - 9*x^8 + 6*x^9 + 4*x^10 + 4*x^11 + 4*x^12). - Colin Barker, Dec 30 2018
EXAMPLE
Some solutions for n=4:
..0..0..0....0..0..0....0..1..0....0..0..1....0..1..0....0..0..0....0..0..0
..1..0..1....1..0..0....0..0..1....0..0..0....1..0..1....0..1..0....1..0..1
..0..1..0....0..0..0....0..1..0....1..0..1....0..1..0....0..0..1....0..1..0
..1..0..0....0..0..0....1..0..1....0..1..0....0..0..1....0..1..0....0..0..1
..0..1..0....0..0..1....0..0..0....1..0..1....0..1..0....1..0..1....0..1..0
..0..0..0....0..0..0....0..0..1....0..1..0....0..0..0....0..0..0....1..0..1
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Aug 14 2015
STATUS
approved