OFFSET
1,1
COMMENTS
Row 2 of A208408.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 18*a(n-1) - 31*a(n-2) - 66*a(n-3) - 24*a(n-4) for n>6.
Empirical g.f.: x*(1 + x)*(2 - 23*x - 3*x^2 + 22*x^3 + 8*x^4) / ((1 - 3*x - 2*x^2)*(1 - 15*x - 12*x^2)). - Colin Barker, Jul 02 2018
EXAMPLE
Some solutions for n=4:
..0..0..0..1....0..1..1..1....0..0..0..0....0..0..1..0....0..0..1..0
..1..1..0..0....0..0..0..1....1..0..2..2....0..0..0..0....2..0..1..2
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Feb 26 2012
STATUS
approved