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A000513
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Number of equivalence classes of n X n matrices over {0,1} with rows and columns summing to 4, where equivalence is defined by row and column permutations. Also number of isomorphism classes of bicolored quartic bipartite graphs, where isomorphism cannot exchange the colors.
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6
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0, 0, 0, 1, 1, 4, 16, 194, 3529, 121790, 5582612, 317579783, 21543414506, 1711281449485, 157117486414656, 16502328443493967, 1965612709107379155, 263512349078757245789, 39497131936385398782814, 6579940884199010139737829, 1211896874083479131415289345, 245593008009270037388205883048
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OFFSET
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1,6
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REFERENCES
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A. Burgess, P. Danziger, E. Mendelsohn, B. Stevens, Orthogonally Resolvable Cycle Decompositions, 2013; http://www.math.ryerson.ca/~andrea.burgess/OCD-submit.pdf
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LINKS
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EXAMPLE
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a(4) = 1:
1111
1111
1111
1111
a(5)=1:
01111
10111
11011
11101
11110
Two of the four examples with n = 6:
111100 . 111100
110011 . 011110
001111 . 001111
111100 . 100111
110011 . 110011
001111 . 111001
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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Eric Rogoyski
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EXTENSIONS
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Offset corrected and a(12) added (from Al-Azemi) by N. J. A. Sloane, Mar 01 2013
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STATUS
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approved
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