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A000512
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Number of equivalence classes of n X n matrices over {0,1} with rows and columns summing to 3, where equivalence is defined by row and column permutations.
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7
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0, 0, 1, 1, 2, 7, 16, 51, 224, 1165, 7454, 56349, 481309, 4548786
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,5
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COMMENTS
| Also, isomorphism classes of bicolored cubic bipartite graphs, where isomorphism cannot exchange the colors.
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REFERENCES
| Goulden and Jackson, Combin. Enum., Wiley, 1983 p. 284.
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LINKS
| Index entries for sequences related to Latin squares and rectangles
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EXAMPLE
| 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. - Michael Steyer (m.steyer(AT)osram.de), Feb 20 2003
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CROSSREFS
| Cf. A000186, A000513, A001501.
A079815 may be an erroneous version of this, or it may have a slightly different (as yet unknown) definition. - N. J. A. Sloane, Sep 04 2010.
Sequence in context: A100099 A164267 A184352 * A084079 A042689 A073998
Adjacent sequences: A000509 A000510 A000511 * A000513 A000514 A000515
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KEYWORD
| nonn,hard,more
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AUTHOR
| Eric Rogoyski
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EXTENSIONS
| Definition corrected by Brendan McKay (bdm(AT)cs.anu.edu.au), May 28 2006
a(1)-a(12) checked by Brendan McKay (bdm(AT)cs.anu.edu.au), Aug 27 2010
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