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A189305
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Number of n X 2 array permutations with each element moving zero or one space diagonally, horizontally or vertically.
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1
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2, 14, 73, 400, 2177, 11854, 64554, 351521, 1914208, 10423761, 56762346, 309097942, 1683185225, 9165743600, 49911830577, 271793641686, 1480045568402, 8059551617921, 43888089440192, 238991507967969, 1301422358761490
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OFFSET
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1,1
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COMMENTS
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LINKS
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FORMULA
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Empirical: a(n) = 4*a(n-1) +8*a(n-2) -4*a(n-4) +a(n-5).
Empirical g.f.: x*(2 + 2*x - x^2)*(1 + 2*x - x^2) / (1 - 4*x - 8*x^2 + 4*x^4 - x^5). - Colin Barker, May 01 2018
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EXAMPLE
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Some solutions for 3 X 2:
..3..1....0..3....0..1....1..3....0..1....0..1....0..1....3..1....1..0....0..1
..2..0....2..1....2..3....0..2....4..3....5..2....4..3....4..0....3..5....3..2
..4..5....4..5....5..4....5..4....2..5....4..3....5..2....2..5....2..4....4..5
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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