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A333732
Number of non-isomorphic n X n binary matrices with equal row and column sums up to permutation of rows and columns and transposition.
1
1, 2, 3, 4, 6, 8, 18, 40, 230, 4296, 431206, 162267272, 201636689772, 777816803942188, 9865957936943931980, 395886667549681689592056, 53716176608076643470621240097, 23524515269630339982914646822137232, 35682168849414944013547274452501783251521
OFFSET
0,2
COMMENTS
Number of simple regular bicolored graphs on 2n unlabeled nodes and allowing the color classes to be interchanged.
First differs from A008324 at n=12. See the note in A004066 by Sean A. Irvine for an explanation of why these two sequences are different.
FORMULA
a(n) = (A333160(n) + A333681(n)) / 2.
a(n) >= A008324(n).
CROSSREFS
KEYWORD
nonn
AUTHOR
Andrew Howroyd, Apr 03 2020
STATUS
approved