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A208403
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Number of n X 3 0..3 arrays with new values 0..3 introduced in row major order and no element equal to more than two of its immediate leftward or upward or right-upward antidiagonal neighbors.
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1
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5, 182, 10682, 667478, 42012698, 2646531062, 166729574522, 10503950018198, 661748758909658, 41690171165650742, 2626480778916392762, 165468289040095516118, 10424502209304556920218, 656743639184636861807222
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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) = 70*a(n-1) - 441*a(n-2) for n>3.
G.f.: x*(5 - 168*x + 147*x^2) / ((1 - 7*x)*(1 - 63*x)).
a(n) = (2/27)*7^(-1+n) * (27+4*9^n) for n>1.
(End)
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EXAMPLE
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Some solutions for n=4:
..0..0..0....0..0..0....0..0..0....0..0..0....0..1..1....0..0..0....0..0..0
..1..1..0....0..1..0....0..1..1....0..1..0....1..0..2....0..1..0....0..1..1
..0..1..0....1..2..1....1..0..0....0..1..1....3..0..1....2..1..1....2..0..2
..0..1..0....0..1..3....0..1..1....2..0..2....1..1..1....2..1..1....2..1..0
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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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