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 A233123 Number of n X 2 0..5 arrays with no element x(i,j) adjacent to itself or value 5-x(i,j) horizontally or vertically, 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). 2
 1, 8, 80, 896, 10496, 124928, 1495040, 17924096, 215023616, 2580021248, 30959206400, 371506282496, 4458058612736, 53496636243968, 641959366492160, 7703511324164096, 92442131595001856, 1109305561960153088 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Column 2 of A233129. LINKS R. H. Hardin, Table of n, a(n) for n = 1..210 FORMULA Empirical: a(n) = 16*a(n-1) - 48*a(n-2). Conjectures from Colin Barker, Mar 19 2018: (Start) G.f.: x*(1 - 8*x) / ((1 - 4*x)*(1 - 12*x)). a(n) = 2^(2*n-3) * (3^n+3) / 3. (End) EXAMPLE Some solutions for n=5: ..0..1....0..1....0..1....0..1....0..1....0..1....0..1....0..1....0..1....0..1 ..1..0....2..5....4..0....4..0....2..0....2..5....4..0....4..0....1..0....1..0 ..0..1....0..4....5..2....2..1....0..2....4..3....2..1....5..2....5..2....5..1 ..1..5....3..0....3..1....1..3....3..5....5..1....4..5....3..5....3..4....1..2 ..0..4....0..2....0..2....2..4....0..4....1..3....0..1....0..2....1..0....0..1 CROSSREFS Sequence in context: A102592 A345081 A320759 * A269796 A328128 A053175 Adjacent sequences:  A233120 A233121 A233122 * A233124 A233125 A233126 KEYWORD nonn AUTHOR R. H. Hardin, Dec 04 2013 STATUS approved

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Last modified June 22 01:32 EDT 2021. Contains 345367 sequences. (Running on oeis4.)