OFFSET
1,2
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 59*a(n-2) - 230*a(n-4) - 2*a(n-6) + 32*a(n-8) for n>10.
Empirical g.f.: 3*x^2*(5 + 45*x - 118*x^2 + 216*x^3 + 94*x^4 + 54*x^5 - 44*x^6 - 16*x^8) / (1 - 59*x^2 + 230*x^4 + 2*x^6 - 32*x^8). - Colin Barker, Sep 22 2018
EXAMPLE
Some solutions for n=5:
..x..0..x..0..x....x..0..x..1..x....x..2..x..0..x....x..0..x..2..x
..2..x..0..x..2....2..x..2..x..1....0..x..0..x..2....2..x..2..x..0
..x..2..x..2..x....x..2..x..1..x....x..2..x..0..x....x..2..x..2..x
..0..x..2..x..1....0..x..1..x..0....2..x..0..x..1....0..x..0..x..1
..x..0..x..1..x....x..1..x..2..x....x..0..x..1..x....x..2..x..1..x
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Oct 27 2013
STATUS
approved