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A208428
Number of n X 2 0..2 arrays with new values 0..2 introduced in row major order and no element equal to any knight-move neighbor (colorings ignoring permutations of colors).
3
2, 14, 54, 216, 864, 3456, 13824, 55296, 221184, 884736, 3538944, 14155776, 56623104, 226492416, 905969664, 3623878656, 14495514624, 57982058496, 231928233984, 927712935936, 3710851743744, 14843406974976, 59373627899904
OFFSET
1,1
COMMENTS
Column 2 of A208434.
FORMULA
Empirical: a(n) = 4*a(n-1) for n>3.
Conjectures from Colin Barker, Feb 23 2018: (Start)
G.f.: 2*x*(1 + 3*x - x^2) / (1 - 4*x).
a(n) = 27*2^(2*n - 5) for n>2.
(End)
EXAMPLE
Some solutions for n=4:
..0..0....0..0....0..0....0..1....0..0....0..0....0..1....0..0....0..0....0..0
..1..1....0..0....1..1....2..1....1..2....0..0....0..2....0..1....1..1....0..0
..1..1....1..2....1..2....2..1....1..2....1..2....2..2....2..1....2..1....1..1
..2..0....1..2....2..2....0..1....0..0....2..2....0..1....2..1....0..2....1..1
CROSSREFS
Cf. A208434.
Sequence in context: A363706 A259125 A067056 * A356373 A137482 A346033
KEYWORD
nonn
AUTHOR
R. H. Hardin, Feb 26 2012
STATUS
approved