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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. 11
0, 0, 1, 1, 2, 7, 16, 51, 224, 1165, 7454, 56349, 481309, 4548786, 46829325, 519812910, 6177695783, 78190425826, 1049510787100, 14886252250208, 222442888670708, 3492326723315796, 57468395960854710, 989052970923320185, 17767732298980160822, 332572885090541084172, 6475438355244504235759, 130954580036269713385884 (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, Feb 20 2003
CROSSREFS
Column k=3 of A133687.
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
KEYWORD
nonn,hard
AUTHOR
Eric Rogoyski
EXTENSIONS
Definition corrected by Brendan McKay, May 28 2006
a(1)-a(12) checked by Brendan McKay, Aug 27 2010
Terms a(15) and beyond from Andrew Howroyd, Apr 01 2020
STATUS
approved

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Last modified March 29 06:15 EDT 2024. Contains 371265 sequences. (Running on oeis4.)