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A321734
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Number of nonnegative integer square matrices with sum of entries equal to n, no zero rows or columns, weakly decreasing row and column sums, and the same row sums as column sums.
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2
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1, 1, 3, 9, 37, 177, 1054, 7237, 57447, 512664, 5101453, 55870885, 668438484, 8667987140, 121123281293, 1814038728900, 28988885491655, 492308367375189, 8854101716492463, 168108959387012804, 3360171602215686668, 70527588239926854144, 1550926052235372201700
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OFFSET
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0,3
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LINKS
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FORMULA
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Let c(y) be the coefficient of m(y) in h(y), where m is monomial symmetric functions and h is homogeneous symmetric functions. Then a(n) = Sum_{|y| = n} c(y).
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EXAMPLE
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The a(3) = 9 matrices:
[3]
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[2 0] [1 1]
[0 1] [1 0]
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[1 0 0] [1 0 0] [0 1 0] [0 1 0] [0 0 1] [0 0 1]
[0 1 0] [0 0 1] [1 0 0] [0 0 1] [1 0 0] [0 1 0]
[0 0 1] [0 1 0] [0 0 1] [1 0 0] [0 1 0] [1 0 0]
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MATHEMATICA
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prs2mat[prs_]:=Table[Count[prs, {i, j}], {i, Union[First/@prs]}, {j, Union[Last/@prs]}];
multsubs[set_, k_]:=If[k==0, {{}}, Join@@Table[Prepend[#, set[[i]]]&/@multsubs[Drop[set, i-1], k-1], {i, Length[set]}]];
Table[Length[Select[multsubs[Tuples[Range[n], 2], n], And[Union[First/@#]==Range[Max@@First/@#]==Union[Last/@#], OrderedQ[Total/@prs2mat[#]], OrderedQ[Total/@Transpose[prs2mat[#]]], Total/@prs2mat[#]==Total/@Transpose[prs2mat[#]]]&]], {n, 5}]
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CROSSREFS
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Cf. A000700, A006052, A007016, A007716, A120732, A319056, A319616, A320451, A321719, A321722, A321732, A321735, A321736, A321739.
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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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