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A222892
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Number of n X 3 0..7 arrays with no element equal to another at a city block distance of exactly two, and new values 0..7 introduced in row major order.
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1
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3, 34, 991, 84521, 11047723, 1639681049, 251412693667, 38863548783281, 6019757701002763, 932903107051648169, 144593771181391763827, 22411792379084676340961, 3473818375479216866296603
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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) = 211*a(n-1) - 9385*a(n-2) + 110913*a(n-3) - 253890*a(n-4) for n>6.
G.f.: x*(3 - 599*x + 21972*x^2 - 138229*x^3 - 495045*x^4 + 558558*x^5) / ((1 - 3*x)*(1 - 14*x)*(1 - 39*x)*(1 - 155*x)).
a(n) = 3^n + 5*2^(n-1)*7^(n-2) + 14*5^(n-3)*31^(n-2) + 10*39^(n-2) for n>2.
(End)
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EXAMPLE
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Some solutions for n=3:
..0..1..2....0..1..1....0..1..2....0..1..2....0..1..2....0..1..2....0..1..2
..3..4..5....0..2..2....3..4..5....3..4..2....2..1..0....3..1..2....3..4..5
..2..0..5....3..3..0....1..6..7....2..0..3....3..4..4....2..0..4....1..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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