OFFSET
1,2
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 17*a(n-2) - 96*a(n-4) + 210*a(n-6) - 152*a(n-8).
Empirical g.f.: x*(1 + 4*x - 10*x^2 - 40*x^3 + 31*x^4 + 120*x^5 - 28*x^6 - 104*x^7) / (1 - 17*x^2 + 96*x^4 - 210*x^6 + 152*x^8). - Colin Barker, Oct 25 2018
EXAMPLE
Some solutions for n=5:
..2..0..0....2..0..0....2..0..0....2..0..0....2..0..0....2..0..0....2..0..0
..1..0..0....1..0..2....1..0..0....1..2..2....1..0..0....2..0..0....2..0..0
..2..0..0....2..0..1....2..0..0....2..1..1....2..0..0....1..0..2....1..0..0
..1..2..2....1..2..2....1..2..2....2..0..0....2..0..0....2..0..1....2..0..0
..2..1..1....2..1..2....2..1..2....1..0..2....1..2..2....1..0..0....1..0..2
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Mar 09 2014
STATUS
approved