OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = a(n-1) + 4*a(n-4) - 4*a(n-5).
Empirical g.f.: x*(33 + 12*x + 16*x^2 + 20*x^3 - 108*x^4) / ((1 - x)*(1 - 2*x^2)*(1 + 2*x^2)). - Colin Barker, Nov 07 2018
EXAMPLE
Some solutions for n=6:
..2....1....0....2....0....2....0....0....1....1....0....0....2....1....1....2
..1....0....1....1....1....1....1....1....0....1....2....0....1....2....2....1
..0....2....0....0....0....1....1....1....2....0....1....1....1....0....2....1
..1....1....1....1....1....0....0....0....1....2....1....1....2....1....1....2
..2....1....2....2....2....2....0....0....1....1....2....2....0....1....1....0
..1....0....1....1....1....1....1....1....2....1....2....2....1....2....0....1
..2....2....2....0....2....1....1....1....0....2....1....1....1....0....2....1
..1....1....1....1....1....0....0....0....1....2....1....1....2....1....1....0
..2....1....0....0....2....2....2....0....1....1....0....0....0....1....1....2
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Sep 18 2014
STATUS
approved