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A189348
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Number of n X 2 array permutations with each element moving one space diagonally, horizontally or vertically.
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1
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1, 4, 13, 45, 160, 565, 2005, 7108, 25209, 89401, 317056, 1124425, 3987721, 14142276, 50154949, 177872293, 630816160, 2237161405, 7933993245, 28137553540, 99788579953, 353895752689, 1255075518976, 4451069407761, 15785519335825
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OFFSET
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1,2
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COMMENTS
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Column 2 of A189355.
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LINKS
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R. H. Hardin, Table of n, a(n) for n = 1..200
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FORMULA
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Empirical: a(n) = 3*a(n-1) +3*a(n-2) -3*a(n-3) -3*a(n-4) +a(n-5).
Empirical g.f.: x*(1 + x - 2*x^2 - 3*x^3 + x^4) / ((1 - x)*(1 - 2*x - 5*x^2 - 2*x^3 + x^4)). - Colin Barker, May 02 2018
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EXAMPLE
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Some solutions for 3 X 2:
..1..3....2..0....3..0....1..0....1..0....3..0....1..0....1..3....1..3....1..0
..0..5....3..1....5..1....4..5....3..5....4..1....4..2....5..0....0..2....3..2
..2..4....5..4....2..4....2..3....2..4....5..2....5..3....2..4....5..4....5..4
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CROSSREFS
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Cf. A189355.
Sequence in context: A320652 A203573 A214997 * A165205 A149431 A149432
Adjacent sequences: A189345 A189346 A189347 * A189349 A189350 A189351
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KEYWORD
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nonn
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AUTHOR
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R. H. Hardin, Apr 20 2011
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STATUS
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approved
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