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

Offset: 0

Author

Andrew Howroyd, Apr 03 2020

Keywords

• nonn

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.

Crossrefs

Cf. A004066, A008324, A333160, A333681.

Formula

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

a(n) >= A008324(n).