OFFSET
1,1
COMMENTS
Row 2 of A223233.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 7*a(n-1) + 30*a(n-2) for n>3.
Conjectures from Colin Barker, Aug 17 2018: (Start)
G.f.: x*(12 - 19*x - 30*x^2) / ((1 + 3*x)*(1 - 10*x)).
a(n) = (-25*(-1)^n*3^(1+n) + 49*10^n) / 65 for n>1.
(End)
EXAMPLE
Some solutions for n=3:
..0..2..1....0..7.11....0..6..2....0..6..5....0..7..3....0..2..1....0..2..0
..0..7..0....3..7..3...10..6..4....4..6..5....3..7..0....6..2..8....8..2..4
Vertex neighbors:
0 -> 1 2 5 6 7
1 -> 0 2 3 7 8
2 -> 0 1 4 6 8
3 -> 1 7 8 9 11
4 -> 2 6 8 9 10
5 -> 0 6 7 10 11
6 -> 0 2 4 5 10
7 -> 0 1 3 5 11
8 -> 1 2 3 4 9
9 -> 3 4 8 10 11
10 -> 4 5 6 9 11
11 -> 3 5 7 9 10
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Mar 18 2013
STATUS
approved