OFFSET
1,1
COMMENTS
Column 3 of A223379.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 221*a(n-2) - 1718*a(n-4) + 1872*a(n-6) for n>7.
Empirical g.f.: 4*x*(17 + 228*x - 449*x^2 - 2200*x^3 + 1290*x^4 + 3168*x^5 - 144*x^6) / (1 - 221*x^2 + 1718*x^4 - 1872*x^6). - Colin Barker, Aug 20 2018
EXAMPLE
Some solutions for n=3:
..1..4..7....6..7..6....5..8..7....7..4..3....3..4..7....8..5..4....8..7..6
..4..7..4....7..6..3....4..7..4....4..3..4....4..7..4....5..4..7....7..6..3
..7..8..5....6..3..6....3..4..7....3..4..5....5..8..5....2..5..8....4..7..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