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 A233175 Number of 2 X n 0..5 arrays with no element x(i,j) adjacent to itself or value 5-x(i,j) horizontally, diagonally or antidiagonally, top left element zero, and 1 appearing before 2 3 and 4, and 2 appearing before 3 in row major order (unlabelled 6-colorings with no clashing color pairs). 1
 3, 8, 80, 800, 8576, 92672, 1009664, 11018240, 120356864, 1315045376, 14370209792, 157036838912, 1716116258816, 18754008252416, 204947383648256, 2239705722650624, 24475955615498240, 267478202279002112 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS R. H. Hardin, Table of n, a(n) for n = 1..210 FORMULA Empirical: a(n) = 12*a(n-1) - 128*a(n-3) for n>4. Conjectures from Colin Barker, Oct 10 2018: (Start) G.f.: x*(3 - 28*x - 16*x^2 + 224*x^3) / ((1 - 4*x)*(1 - 8*x - 32*x^2)). a(n) = 2^(2*n-3) + (1/32)*sqrt(3)*(-(4-4*sqrt(3))^n + (4*(1+sqrt(3)))^n) for n>1. (End) EXAMPLE Some solutions for n=5: ..0..1..5..4..0....0..1..0..2..0....0..1..0..1..0....0..1..2..1..2 ..2..1..3..1..3....5..3..5..2..4....2..4..0..2..5....5..1..3..5..3 CROSSREFS Row 2 of A233174. Sequence in context: A060752 A347641 A287389 * A347920 A367273 A070901 Adjacent sequences: A233172 A233173 A233174 * A233176 A233177 A233178 KEYWORD nonn AUTHOR R. H. Hardin, Dec 05 2013 STATUS approved

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Last modified September 12 18:10 EDT 2024. Contains 375853 sequences. (Running on oeis4.)