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A229443
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Number of nX6 0..2 arrays with horizontal differences mod 3 never 1, vertical differences mod 3 never -1, and rows and columns lexicographically nondecreasing
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1
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8, 25, 93, 387, 1609, 6374, 23610, 81177, 258698, 765702, 2113491, 5467941, 13331626, 30795942, 67738085, 142526854, 288060848, 561310955, 1057997269, 1934623043, 3440842683, 5966088386, 10105555904, 16752093179, 27222289586
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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) = (73/159667200)*n^12 - (19/26611200)*n^11 + (19/2903040)*n^10 + (47/161280)*n^9 - (1259/1612800)*n^8 + (7711/806400)*n^7 - (10715/580608)*n^6 + (30575/96768)*n^5 - (4597853/3628800)*n^4 + (1198483/201600)*n^3 - (621689/55440)*n^2 + (168439/9240)*n - 4
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EXAMPLE
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Some solutions for n=4
..0..0..0..2..2..2....0..0..2..2..2..2....0..0..0..2..2..2....0..0..2..2..2..2
..1..1..1..0..0..2....0..0..2..2..2..2....1..1..1..0..2..2....1..1..0..0..0..2
..1..1..1..1..1..0....1..1..0..2..2..2....1..1..1..1..0..2....2..2..1..1..1..0
..2..2..2..1..1..1....1..1..1..0..2..2....2..2..2..2..1..0....2..2..2..2..2..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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