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A331197
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Number of nonnegative integer matrices with 2 distinct columns and any number of nonzero rows with each column sum being n and rows in nonincreasing lexicographic order.
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3
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0, 1, 7, 28, 104, 332, 1032, 2983, 8384, 22622, 59479, 151902, 379616, 927521, 2224100, 5236410, 12130549, 27669296, 62229605, 138095206, 302672402, 655627183, 1404598865, 2977830134, 6251059210, 12999297747, 26791987616, 54750232180, 110977385294, 223204454700, 445590973235
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OFFSET
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0,3
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COMMENTS
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The condition that the rows be in nonincreasing order is equivalent to considering nonequivalent matrices up to permutation of rows.
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LINKS
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FORMULA
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EXAMPLE
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The a(2) = 7 matrices are:
[2 1] [2 0] [1 2] [1 1] [2 0] [1 0] [1 0]
[0 1] [0 2] [1 0] [1 0] [0 1] [1 0] [1 0]
[0 1] [0 1] [0 2] [0 1]
[0 1]
See the example in A331197 for the a(3) = 28 case.
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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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