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A145052
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One-third of the number of n X n nonnegative integer arrays with every 3 X 3 subblock summing to 1.
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0
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3, 7, 11, 15, 27, 39, 51, 87, 123, 159, 267, 375, 483, 807, 1131, 1455, 2427, 3399, 4371, 7287, 10203, 13119, 21867, 30615
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OFFSET
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3,1
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COMMENTS
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First differences of (a(3k), a(3k + 1)), (a(3k + 1), a(3k + 2)), (a(3k + 2), a(3k + 3)) seem to be 4 * 3^(k - 1). - David A. Corneth, Apr 15 2015
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LINKS
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FORMULA
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Conjectured formula: a(n) = 6*(3^(floor(n / 3))/3 - 1) + 3 + 4 * (n mod 3) * 3^(floor(n / 3))/3. - David A. Corneth, Apr 15 2015
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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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