OFFSET
1,1
COMMENTS
Row 3 of A223331.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 18*a(n-1) - 27*a(n-2) for n>4.
Conjectures from Colin Barker, Aug 19 2018: (Start)
G.f.: x*(64 - 909*x + 1323*x^2 - 54*x^3) / (1 - 18*x + 27*x^2).
a(n) = (49/54)*((9-3*sqrt(6))^n + (3*(3+sqrt(6)))^n) for n>2.
(End)
EXAMPLE
Some solutions for n=3:
0 2 6 0 4 6 0 2 6 0 1 5 0 2 3 0 1 5 0 2 6
6 7 6 6 2 3 3 7 5 5 4 6 3 7 6 5 7 3 0 4 0
3 7 6 6 2 0 6 4 6 6 2 0 6 7 3 6 7 6 6 4 6
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