A223289 4-loop graph coloring a rectangular array: number of n X n 0..8 arrays where 0..8 label nodes of a graph with edges 0,1 1,2 2,0 0,3 3,4 4,0 0,5 5,6 6,0 0,7 7,8 8,0 and every array movement to a horizontal or vertical neighbor moves along an edge of this graph.

9, 168, 42168, 46008720, 757664837832, 53263771547091072, 56395315109321439563328, 254765586321230138822186989968, 17333186258617759005034608109179216168

Offset

1,1

Comments

Diagonal of A223297.

Links

R. H. Hardin, Table of n, a(n) for n = 1..10

Example

Some solutions for 3 X 3
..0..1..0..5....0..3..0..7....0..3..0..3....0..3..0..6....1..0..8..0
..2..0..1..0....3..0..6..0....2..0..8..0....2..0..2..0....0..3..0..5
..0..6..0..1....0..2..0..6....0..1..0..1....0..8..0..1....4..0..4..0

Crossrefs

Cf. A223297.

Sequence in context: A367139 A180819 A132874 * A281996 A017306 A210089

Adjacent sequences: A223286 A223287 A223288 * A223290 A223291 A223292

Keyword

nonn

Author

R. H. Hardin, Mar 19 2013

Status

approved