A223250 Two-loop graph coloring a rectangular array: number of n X 3 0..4 arrays where 0..4 label nodes of a graph with edges 0,1 1,2 2,0 0,3 3,4 4,0 and every array movement to a horizontal or vertical neighbor moves along an edge of this graph.

32, 236, 2172, 17828, 166892, 1382228, 12894316, 107283636, 996653548, 8326150836, 77047324460, 646086687220, 5957011569772, 50127570610868, 460630428892844, 3888717399278196, 35622664419652844, 301636706357260340

Offset

1,1

Comments

Column 3 of A223255.

Links

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

Formula

Empirical: a(n) = 2*a(n-1) +75*a(n-2) -126*a(n-3) -70*a(n-4) +48*a(n-5).

Empirical g.f.: -4*x*(78*x^4 -46*x^3 -175*x^2 +43*x +8) / (48*x^5 -70*x^4 -126*x^3 +75*x^2 +2*x -1). - Colin Barker, May 03 2014

Example

Some solutions for n=3:
..3..0..1....4..0..3....3..4..3....1..0..4....4..3..4....1..0..3....1..0..3
..0..2..0....0..2..0....4..3..4....0..1..0....0..4..3....0..1..0....0..2..0
..4..0..2....2..0..3....3..4..0....3..0..2....3..0..4....3..0..1....2..0..2

Crossrefs

Sequence in context: A301889 A302085 A229400 * A250748 A333268 A060622

Adjacent sequences: A223247 A223248 A223249 * A223251 A223252 A223253

Keyword

nonn

Author

R. H. Hardin, Mar 18 2013

Status

approved