OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..36
FORMULA
Empirical: a(n) = 4*a(n-2) + 25*a(n-4) - 100*a(n-6) for n>11.
Empirical g.f.: x*(81 + 636*x + 986*x^2 - 532*x^3 - 2643*x^4 - 14580*x^5 - 24794*x^6 + 20120*x^7 + 44610*x^8 + 1100*x^9 - 4392*x^10) / ((1 - 2*x)*(1 + 2*x)*(1 - 5*x^2)*(1 + 5*x^2)). - Colin Barker, Oct 23 2018
EXAMPLE
Some solutions for n=5:
..1..0..0..1..2..1....1..0..2..1..0..1....2..1..0..1..2..2....1..0..1..2..0..1
..1..0..1..2..0..0....1..2..0..0..0..2....0..2..0..0..0..2....2..0..0..0..2..1
..0..0..2..1..0..1....2..1..0..1..2..1....0..1..2..1..0..1....1..2..1..0..1..2
..1..2..0..0..0..2....0..0..0..2..1..0....0..0..0..2..0..0....0..0..2..0..0..0
..2..1..0..1..2..0....0..1..2..0..0..0....2..1..0..1..2..1....1..0..1..2..1..0
..0..0..0..2..1..0....1..2..1..0..2..1....2..1..0..0..0..2....2..0..0..0..2..1
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Feb 10 2014
STATUS
approved