login
Petersen graph (3,1) coloring a rectangular array: number of n X 5 0..5 arrays where 0..5 label nodes of a graph with edges 0,1 0,3 3,5 3,4 1,2 1,4 4,5 2,0 2,5 and every array movement to a horizontal or antidiagonal neighbor moves along an edge of this graph, with the array starting at 0.
1

%I #8 Aug 21 2018 06:30:08

%S 81,6939,609309,53599905,4715559621,414863325945,36498667573629,

%T 3211064180380305,282501632829717621,24853807982558115945,

%U 2186577702401491603629,192369799106697718450305

%N Petersen graph (3,1) coloring a rectangular array: number of n X 5 0..5 arrays where 0..5 label nodes of a graph with edges 0,1 0,3 3,5 3,4 1,2 1,4 4,5 2,0 2,5 and every array movement to a horizontal or antidiagonal neighbor moves along an edge of this graph, with the array starting at 0.

%C Column 5 of A223556.

%H R. H. Hardin, <a href="/A223553/b223553.txt">Table of n, a(n) for n = 1..210</a>

%F Empirical: a(n) = 95*a(n-1) - 626*a(n-2) + 720*a(n-3) for n>4.

%F Empirical g.f.: 9*x*(9 - 84*x + 90*x^2 + 116*x^3) / (1 - 95*x + 626*x^2 - 720*x^3). - _Colin Barker_, Aug 21 2018

%e Some solutions for n=3:

%e ..0..2..5..3..0....0..1..0..1..4....0..2..1..4..5....0..2..0..3..0

%e ..0..2..5..2..1....0..1..2..5..3....0..2..1..4..1....0..2..0..2..5

%e ..1..4..1..2..1....2..1..2..0..1....1..4..1..2..0....1..2..1..2..0

%Y Cf. A223556.

%K nonn

%O 1,1

%A _R. H. Hardin_, Mar 22 2013