OFFSET
1,1
COMMENTS
Column 5 of A223331.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 117*a(n-1) - 294*a(n-2).
Empirical g.f.: 27*x*(3 - 8*x) / (1 - 117*x + 294*x^2). - Colin Barker, Aug 19 2018
EXAMPLE
Some solutions for n=3:
..0..2..0..2..6....0..4..6..4..0....0..4..5..7..6....0..4..0..2..3
..0..2..0..2..6....6..2..0..4..0....0..4..6..4..6....6..2..6..2..0
..0..2..6..4..0....0..2..0..1..3....0..2..0..2..0....0..2..3..2..0
Vertex neighbors:
0 -> 1 2 4
1 -> 0 3 5
2 -> 0 3 6
3 -> 1 2 7
4 -> 0 5 6
5 -> 1 4 7
6 -> 2 4 7
7 -> 3 5 6
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Mar 19 2013
STATUS
approved