OFFSET
1,2
COMMENTS
Column 2 of A221804.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..70
FORMULA
Empirical: a(n) = 8*a(n-1) - 8*a(n-2) - 10*a(n-3) + 4*a(n-4) - 7*a(n-5) + 4*a(n-6).
Empirical g.f.: x^2*(9 - 16*x + 2*x^2 - 11*x^3 + 4*x^4) / (1 - 8*x + 8*x^2 + 10*x^3 - 4*x^4 + 7*x^5 - 4*x^6). - Colin Barker, Aug 11 2018
EXAMPLE
Some solutions for n=3:
..1..1....1..0....1..1....2..1....1..0....0..1....0..1....1..1....0..2....0..0
..2..0....2..2....3..1....2..1....4..1....1..2....1..3....2..0....1..1....0..4
..2..0....0..1....0..0....0..0....0..0....2..0....0..1....1..1....1..1....1..1
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Jan 26 2013
STATUS
approved