OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 16*a(n-2) + 3*a(n-4) - 10*a(n-6) + 24*a(n-8) - 16*a(n-10).
Empirical g.f.: 2*x*(4 + 8*x - 13*x^2 - 12*x^3 + 13*x^4 + 4*x^5 - 16*x^6 + 8*x^8) / (1 - 16*x^2 - 3*x^4 + 10*x^6 - 24*x^8 + 16*x^10). - Colin Barker, Sep 23 2018
EXAMPLE
Some solutions for n=4:
..x..0..x..0..x....x..0..x..0..x....x..0..x..0..x....x..0..x..0..x
..1..x..1..x..3....3..x..1..x..3....1..x..3..x..1....1..x..1..x..3
..x..2..x..0..x....x..0..x..2..x....x..2..x..2..x....x..2..x..0..x
..3..x..1..x..3....3..x..1..x..3....0..x..0..x..1....1..x..3..x..1
..x..0..x..2..x....x..2..x..0..x....x..1..x..3..x....x..0..x..2..x
..3..x..3..x..1....1..x..1..x..3....0..x..2..x..2....3..x..1..x..1
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Nov 01 2013
STATUS
approved