OFFSET
1,1
COMMENTS
Column 7 of A207149.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = a(n-1) + 2*a(n-2) - 2*a(n-3) for n>14.
Empirical g.f.: x*(315 - 97*x - 229*x^2 + 9*x^3 + 2*x^4 - 2*x^5 + 8*x^6 - 8*x^7 - 16*x^8 + 16*x^9 - 16*x^10 + 16*x^11 - 16*x^12 + 16*x^13) / ((1 - x)*(1 - 2*x^2)). - Colin Barker, Jun 19 2018
EXAMPLE
Some solutions for n=4:
..2..2..0..1..0..1..0..1....0..2..0..1..0..1..0..1....1..0..1..0..2..0..1..0
..1..0..2..0..1..0..1..0....2..0..2..0..1..0..1..0....0..1..0..1..0..2..0..1
..0..1..0..2..0..1..0..1....0..2..0..2..0..1..0..1....1..0..1..0..1..0..2..0
..2..0..1..0..2..0..1..0....1..0..2..0..2..0..1..0....0..1..0..1..0..1..0..2
..0..2..0..1..0..2..0..1....0..1..0..2..0..2..0..1....2..0..1..0..1..0..1..1
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Feb 15 2012
STATUS
approved