A333732 - OEIS

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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, 2, 3, 4, 6, 8, 18, 40, 230, 4296, 431206, 162267272, 201636689772, 777816803942188, 9865957936943931980, 395886667549681689592056, 53716176608076643470621240097, 23524515269630339982914646822137232, 35682168849414944013547274452501783251521

(list; graph; refs; listen; history; text; internal format)

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.

LINKS

Table of n, a(n) for n=0..18.

FORMULA

a(n) = (A333160(n) + A333681(n)) / 2.

a(n) >= A008324(n).

CROSSREFS

Cf. A004066, A008324, A333160, A333681.

Sequence in context: A333160 A345250 A008324 * A274456 A333681 A084074

Adjacent sequences: A333729 A333730 A333731 * A333733 A333734 A333735

KEYWORD

nonn

AUTHOR

Andrew Howroyd, Apr 03 2020

STATUS

approved