OFFSET
1,1
COMMENTS
Column 6 of A223331.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 282*a(n-1) - 3969*a(n-2) + 9604*a(n-3).
Empirical g.f.: 27*x*(9 - 137*x + 294*x^2) / (1 - 282*x + 3969*x^2 - 9604*x^3). - Colin Barker, Aug 19 2018
EXAMPLE
Some solutions for n=3:
..0..4..0..4..6..2....0..4..0..1..0..1....0..4..6..7..5..1....0..4..0..1..5..4
..0..4..0..2..0..2....0..4..5..4..5..4....0..4..5..4..0..1....0..4..5..4..6..7
..0..4..6..4..0..2....0..4..5..4..5..4....0..4..5..4..0..2....0..4..5..4..5..7
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