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Search: id:A079815
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| A079815 |
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Number of equivalent classes of n X n 0-1 matrices with 3 1's in each row and column. |
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+0
1
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OFFSET
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3,3
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COMMENT
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Matrices are considered to belong to one equivalent class if they can be transformed into each other by successive permutations of rows or columns.
In general, to transform 2 equivalent matrices into each other, it is necessary to first permute rows, then columns, then rows and so on.
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EXAMPLE
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n=4: every matrix with 3 1's in each row and column can be transformed by permutation of rows (or columns) into {1110,1101,1011,0111}, therefore a(4)=1.
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CROSSREFS
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Cf. A001501.
Sequence in context: A042689 A073998 A129444 this_sequence A006883 A023269 A023300
Adjacent sequences: A079812 A079813 A079814 this_sequence A079816 A079817 A079818
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KEYWORD
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more,nonn
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AUTHOR
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Michael Steyer (m.steyer(AT)osram.de), Feb 20 2003
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