A223418 3-level binary fanout graph coloring a rectangular array: number of n X 3 0..6 arrays where 0..6 label nodes of a graph with edges 0,1 1,3 1,4 0,2 2,5 2,6 and every array movement to a horizontal or vertical neighbor moves along an edge of this graph.

26, 136, 868, 4720, 29912, 163168, 1033328, 5638336, 35704800, 194827648, 1233740224, 6732071680, 42630619008, 232619832832, 1473057249024, 8037939530752, 50899980869120, 277742748522496, 1758796582951936

Offset: 1

Author

R. H. Hardin, Mar 20 2013

Keywords

• nonn

Comments

Column 3 of A223423.

Examples

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

Links

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

Crossrefs

Cf. A223423.

Formula

Empirical: a(n) = 38*a(n-2) - 120*a(n-4) + 32*a(n-6).

Empirical g.f.: 2*x*(13 + 68*x - 60*x^2 - 224*x^3 + 24*x^4 + 64*x^5) / (1 - 38*x^2 + 120*x^4 - 32*x^6). - Colin Barker, Aug 20 2018