The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A000512 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. 9
 0, 0, 1, 1, 2, 7, 16, 51, 224, 1165, 7454, 56349, 481309, 4548786 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,5 COMMENTS Also, isomorphism classes of bicolored cubic bipartite graphs, where isomorphism cannot exchange the colors. REFERENCES A. Burgess, P. Danziger, E. Mendelsohn, B. Stevens, Orthogonally Resolvable Cycle Decompositions, 2013; http://www.math.ryerson.ca/~andrea.burgess/OCD-submit.pdf Goulden and Jackson, Combin. Enum., Wiley, 1983 p. 284. LINKS 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 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: A248114 A330227 A322192 * A084079 A286848 A239425 Adjacent sequences:  A000509 A000510 A000511 * A000513 A000514 A000515 KEYWORD nonn,hard,more AUTHOR Eric Rogoyski EXTENSIONS Definition corrected by Brendan McKay, May 28 2006 a(1)-a(12) checked by Brendan McKay, Aug 27 2010 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified February 24 06:13 EST 2020. Contains 332199 sequences. (Running on oeis4.)