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A206353
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Number of n X 2 0..4 arrays with no element equal to another within two positions in the same row or column, and new values 0..4 introduced in row major order.
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1
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1, 4, 17, 120, 884, 6558, 48680, 361422, 2683328, 19922214, 147910952, 1098154590, 8153170064, 60532632918, 449420225720, 3336688521102, 24773006668448, 183925426722054, 1365541253642312, 10138363949208510, 75271562311604144
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OFFSET
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1,2
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COMMENTS
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LINKS
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FORMULA
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Empirical: a(n) = 6*a(n-1) + 13*a(n-2) - 18*a(n-3) for n>5.
Empirical g.f.: x*(1 - 2*x - 20*x^2 - 16*x^3 + 15*x^4) / ((1 - x)*(1 - 5*x - 18*x^2)). - Colin Barker, Jun 15 2018
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EXAMPLE
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Some solutions for n=4:
..0..1....0..1....0..1....0..1....0..1....0..1....0..1....0..1....0..1....0..1
..1..0....1..2....2..3....1..0....1..2....1..0....2..3....1..2....2..3....1..0
..2..3....2..0....3..2....2..3....3..4....2..3....1..4....2..3....4..2....2..3
..3..4....3..4....4..0....4..1....2..3....3..1....0..1....3..0....0..1....0..4
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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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