OFFSET
1,1
COMMENTS
Column 4 of A207149.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = a(n-1) + 2*a(n-2) - 2*a(n-3) for n>11.
Empirical g.f.: x*(62 + 33*x - 109*x^2 + 14*x^3 - 2*x^4 - 4*x^5 + 4*x^6 - 4*x^7 + 4*x^8 - 4*x^9 + 4*x^10) / ((1 - x)*(1 - 2*x^2)). - Colin Barker, Jun 19 2018
EXAMPLE
Some solutions for n=4:
..2..1..0..2..0....2..2..0..1..0....2..1..1..0..2....0..1..0..1..0
..1..0..1..0..2....1..0..2..0..1....1..1..0..1..0....1..0..1..0..1
..0..1..0..1..0....0..1..0..2..0....1..0..1..0..1....0..1..0..1..0
..2..0..1..0..1....1..0..1..0..2....0..1..0..1..0....1..0..1..0..1
..0..2..0..1..1....0..1..0..1..1....1..0..1..0..1....0..1..0..1..2
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Feb 15 2012
STATUS
approved