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 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. 1
 9, 24, 96, 288, 1056, 3360, 11808, 38688, 133152, 442656, 1507872, 5049120, 17112096, 57505056, 194401824, 654442272, 2209656864, 7445195040, 25122449952, 84684010272, 285663609888, 963135692064, 3248444571168, 10953530107680 (list; graph; refs; listen; history; text; internal format)
 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 A050282 A096757 Adjacent sequences:  A223287 A223288 A223289 * A223291 A223292 A223293 KEYWORD nonn AUTHOR R. H. Hardin, Mar 19 2013 STATUS approved

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Last modified December 7 09:33 EST 2019. Contains 329843 sequences. (Running on oeis4.)