OFFSET
1,1
COMMENTS
Column 2 of A221688.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..23
FORMULA
Empirical: a(n) = 13*a(n-1) - 18*a(n-2) - 29*a(n-3) - 15*a(n-4) - 12*a(n-5) - 2*a(n-6).
Empirical g.f.: x*(3 - 4*x - 5*x^2 - 2*x^3 - 2*x^4) / (1 - 13*x + 18*x^2 + 29*x^3 + 15*x^4 + 12*x^5 + 2*x^6). - Colin Barker, Aug 10 2018
EXAMPLE
Some solutions for n=3:
..0..0....2..0....0..0....0..1....0..0....1..1....0..0....0..1....1..1....2..0
..2..4....1..2....3..2....3..1....3..2....2..0....6..0....2..2....2..0....0..4
..0..0....0..1....0..1....0..1....1..0....0..2....0..0....0..1....2..0....0..0
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Jan 22 2013
STATUS
approved