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A207389
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Number of n X 6 0..1 arrays avoiding 0 0 1 and 0 1 0 horizontally and 0 0 1 and 1 1 0 vertically.
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1
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21, 441, 2307, 7561, 19319, 42167, 82477, 148743, 251937, 405885, 627663, 938013, 1361779, 1928363, 2672201, 3633259, 4857549, 6397665, 8313339, 10672017, 13549455, 17030335, 21208901, 26189615, 32087833, 39030501, 47156871, 56619237
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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) = (1/36)*n^6 + (113/60)*n^5 + (151/9)*n^4 + (95/4)*n^3 - (605/36)*n^2 - (229/30)*n + 3.
G.f.: x*(21 + 294*x - 339*x^2 - 62*x^3 + 139*x^4 - 36*x^5 + 3*x^6) / (1 - x)^7.
a(n) = 7*a(n-1) - 21*a(n-2) + 35*a(n-3) - 35*a(n-4) + 21*a(n-5) - 7*a(n-6) + a(n-7) for n>7.
(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....1..1..1..1..1..1....1..1..0..0..0..0
..0..1..1..1..0..1....1..1..1..1..1..0....1..1..1..1..0..1....1..0..1..1..0..1
..0..1..1..0..0..0....1..1..0..1..1..0....1..1..1..1..1..1....1..1..1..1..0..1
..0..1..1..0..0..0....1..1..1..1..1..0....1..1..1..1..0..1....1..1..1..1..0..1
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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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