OFFSET
1,1
COMMENTS
Column 2 of A223379.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 7*a(n-1) - 4*a(n-2).
Empirical g.f.: 24*x*(1 - x) / (1 - 7*x + 4*x^2). - Colin Barker, Mar 16 2018
EXAMPLE
Some solutions for n=3:
..0..3....6..3....4..5....1..0....3..6....4..3....4..5....3..4....5..4....5..4
..1..4....7..4....7..4....4..3....6..7....5..4....1..2....4..7....4..3....4..3
..0..1....6..7....6..3....3..0....7..8....2..1....4..1....5..4....5..4....3..6
Vertex neighbors:
0 -> 1 3
1 -> 0 2 4
2 -> 1 5
3 -> 0 4 6
4 -> 3 1 5 7
5 -> 4 2 8
6 -> 3 7
7 -> 6 4 8
8 -> 7 5
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Mar 19 2013
STATUS
approved