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A195639
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Number of lower triangles of an n X n 0..3 array with all row sums equal to the length of the row and all column sums equal to the length of the column.
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1
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1, 1, 3, 19, 379, 22506, 4063437, 2303397986, 4165684145897, 24351094470461293, 465231630106636264261, 29310412705455253400706632, 6135104108066245513806738233622, 4293669524764808720927311131475805624, 10102086274414407316013385512463577654333437
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OFFSET
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1,3
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LINKS
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EXAMPLE
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Some solutions for n=4:
..1........1........1........1........1........1........1........1
..0.2......0.2......1.1......2.0......2.0......0.2......0.2......1.1
..0.1.2....3.0.0....2.0.1....1.2.0....1.0.2....2.1.0....3.0.0....2.0.1
..3.0.0.1..0.1.2.1..0.2.1.1..0.1.2.1..0.3.0.1..1.0.2.1..0.1.2.1..0.2.1.1
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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