OFFSET
1,1
COMMENTS
Column 1 of A206238.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 8*a(n-1) -11*a(n-2) +36*a(n-3) -303*a(n-4) +232*a(n-5) +147*a(n-6) +756*a(n-7) for n>8.
Empirical g.f.: x*(15 - 60*x - 5*x^2 - 720*x^3 + 1585*x^4 + 1366*x^5 + 2793*x^6 - 378*x^7) / ((1 - 4*x)*(1 - x - x^2 - 3*x^3)*(1 - 3*x - 7*x^2 - 63*x^3)). - Colin Barker, Jun 14 2018
EXAMPLE
Some solutions for n=4:
..0..1....0..0....0..1....0..0....0..0....0..1....0..1....0..0....0..0....0..0
..0..0....0..1....0..0....0..1....1..0....2..1....2..0....1..1....0..1....0..1
..0..1....1..2....0..1....1..0....0..1....3..1....0..0....2..1....1..2....1..2
..1..2....1..1....1..0....0..0....0..0....0..1....3..0....1..0....2..2....1..1
..1..1....0..1....0..0....2..2....0..2....3..3....2..1....0..0....1..1....0..0
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Feb 05 2012
STATUS
approved