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A233257
Number of 2 X n 0..5 arrays with no element x(i,j) adjacent to itself or value 5-x(i,j) horizontally 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, 10, 104, 1184, 13952, 166400, 1992704, 23896064, 286687232, 3439984640, 41278767104, 495341010944, 5944075354112, 71328837140480, 855945777250304, 10271348253261824, 123256174744174592, 1479074079750225920
OFFSET
1,1
LINKS
FORMULA
Empirical: a(n) = 16*a(n-1) - 48*a(n-2) for n>3.
Conjectures from Colin Barker, Oct 11 2018: (Start)
G.f.: x*(3 - 38*x + 88*x^2) / ((1 - 4*x)*(1 - 12*x)).
a(n) = 2^(2*n-3) * (4*3^n+9) / 9 for n>1.
(End)
EXAMPLE
Some solutions for n=5:
..0..1..2..5..3....0..1..2..4..3....0..1..5..4..2....0..1..2..1..0
..0..4..2..1..2....5..1..5..4..2....2..4..3..1..2....2..1..5..4..0
CROSSREFS
Row 2 of A233256.
Sequence in context: A025541 A203903 A173325 * A261127 A083108 A117664
KEYWORD
nonn
AUTHOR
R. H. Hardin, Dec 06 2013
STATUS
approved