A223290 4-loop graph coloring a rectangular array: number of n X 1 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, 24, 96, 288, 1056, 3360, 11808, 38688, 133152, 442656, 1507872, 5049120, 17112096, 57505056, 194401824, 654442272, 2209656864, 7445195040, 25122449952, 84684010272, 285663609888, 963135692064, 3248444571168, 10953530107680

Offset

1,1

Comments

Column 1 of A223297.

Links

R. H. Hardin, Table of n, a(n) for n = 1..210

Formula

Empirical: a(n) = a(n-1) + 8*a(n-2).

Empirical g.f.: 3*x*(3 + 5*x) / (1 - x - 8*x^2). - Colin Barker, Aug 19 2018

Example

Some solutions for n=3:
..0....0....2....3....3....6....7....0....5....7....2....5....4....6....7....0
..6....7....0....0....0....0....0....1....6....8....0....0....0....0....0....4
..5....0....4....7....2....4....1....0....5....0....3....4....2....1....2....3

Crossrefs

Cf. A223297.

Sequence in context: A195970 A223372 A180334 * A121089 A362697 A050282

Adjacent sequences: A223287 A223288 A223289 * A223291 A223292 A223293

Keyword

nonn

Author

R. H. Hardin, Mar 19 2013

Status

approved