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 A000513 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. 6
 0, 0, 0, 1, 1, 4, 16, 194, 3529, 121790, 5582612, 317579783, 21543414506, 1711281449485, 157117486414656, 16502328443493967, 1965612709107379155, 263512349078757245789, 39497131936385398782814, 6579940884199010139737829, 1211896874083479131415289345, 245593008009270037388205883048 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,6 REFERENCES A. Burgess, P. Danziger, E. Mendelsohn, B. Stevens, Orthogonally Resolvable Cycle Decompositions, 2013; http://www.math.ryerson.ca/~andrea.burgess/OCD-submit.pdf LINKS A. Al-Azemi, Isomorph-rejection: theory and an application, Kuwait J. Sci., 39 (2A) (2012), 1-14. - From N. J. A. Sloane, Mar 01 2013 A. Burgess, P. Danziger, E. Mendelsohn, B. Stevens, Orthogonally Resolvable Cycle Decompositions, Journal of Combinatorial Designs, Volume 23, Issue 8, August 2015, Pages 328-351. EXAMPLE 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 CROSSREFS Column k=4 of A133687. Cf. A000512. Sequence in context: A012921 A280468 A224802 * A088027 A271267 A333438 Adjacent sequences:  A000510 A000511 A000512 * A000514 A000515 A000516 KEYWORD nonn AUTHOR Eric Rogoyski EXTENSIONS Definition corrected by Brendan McKay, May 28 2006 Offset corrected and a(12) added (from Al-Azemi) by N. J. A. Sloane, Mar 01 2013 Terms a(13) and beyond from Andrew Howroyd, Apr 01 2020 STATUS approved

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Last modified May 28 12:02 EDT 2020. Contains 334681 sequences. (Running on oeis4.)