OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 12*a(n-2) - 24*a(n-4) + 31*a(n-6) - 16*a(n-8).
Empirical g.f.: 2*x*(1 + 2*x - 3*x^2 - 2*x^3 + 8*x^4 + 6*x^5 - 6*x^6 - 4*x^7) / (1 - 12*x^2 + 24*x^4 - 31*x^6 + 16*x^8). - Colin Barker, Oct 27 2018
EXAMPLE
Some solutions for n=4:
..3..3....1..1....1..1....1..1....3..3....1..1....1..1....1..1....3..3....1..1
..3..0....1..2....1..0....1..0....3..2....1..0....1..2....1..2....3..2....1..0
..3..0....1..2....3..2....1..0....1..1....1..0....3..2....3..2....3..0....3..0
..1..2....3..0....1..2....3..0....3..3....3..2....1..1....1..2....1..0....1..2
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Apr 03 2014
STATUS
approved