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%I #8 Aug 19 2018 06:13:03
%S 9,24,96,288,1056,3360,11808,38688,133152,442656,1507872,5049120,
%T 17112096,57505056,194401824,654442272,2209656864,7445195040,
%U 25122449952,84684010272,285663609888,963135692064,3248444571168,10953530107680
%N 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.
%C Column 1 of A223297.
%H R. H. Hardin, <a href="/A223290/b223290.txt">Table of n, a(n) for n = 1..210</a>
%F Empirical: a(n) = a(n-1) + 8*a(n-2).
%F Empirical g.f.: 3*x*(3 + 5*x) / (1 - x - 8*x^2). - _Colin Barker_, Aug 19 2018
%e Some solutions for n=3:
%e ..0....0....2....3....3....6....7....0....5....7....2....5....4....6....7....0
%e ..6....7....0....0....0....0....0....1....6....8....0....0....0....0....0....4
%e ..5....0....4....7....2....4....1....0....5....0....3....4....2....1....2....3
%Y Cf. A223297.
%K nonn
%O 1,1
%A _R. H. Hardin_, Mar 19 2013
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