OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 4*a(n-4) for n>13.
Empirical g.f.: x*(7353 + 5034*x + 2478*x^2 + 3496*x^3 - 24054*x^4 - 13408*x^5 - 652*x^6 + 32*x^7 - 862*x^8 - 528*x^10 + 288*x^12) / ((1 - 2*x^2)*(1 + 2*x^2)). - Colin Barker, Oct 20 2018
EXAMPLE
Some solutions for n=5:
..1..2..0..0..0..2....2..1..0..1..2..2....2..0..0..0..2..1....2..0..0..0..1..2
..2..1..0..1..2..1....1..2..0..0..0..1....1..2..1..0..1..2....1..2..1..0..1..2
..0..0..0..2..1..0....0..1..2..1..0..1....0..1..2..0..0..0....0..1..2..0..0..0
..0..1..2..0..0..0....0..0..0..2..0..0....0..0..0..2..1..0....0..0..0..2..1..0
..0..2..1..0..1..2....2..1..0..1..2..1....2..1..0..1..2..0....1..1..0..1..2..1
..2..1..0..0..2..2....2..2..0..0..0..2....0..2..0..0..0..2....2..2..0..0..1..2
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Jan 17 2014
STATUS
approved