A331717 Number of nonequivalent n-column binary matrices with 2 ones in every column and any number of distinct nonzero rows up to permutation of rows and columns.

1, 0, 1, 4, 12, 36, 124, 412, 1500

Offset

0,4

Links

Table of n, a(n) for n=0..8.

Example

The a(3) = 4 matrices are:
  [1 1 1]  [1 1 0]  [1 1 1]  [1 1 0]
  [1 0 0]  [1 0 1]  [1 1 0]  [1 0 1]
  [0 1 0]  [0 1 0]  [0 0 1]  [0 1 1]
  [0 0 1]  [0 0 1]

Crossrefs

Row n=2 of A331510.

Cf. A331718.

Sequence in context: A055395 A113990 A231179 * A192010 A252697 A056383

Adjacent sequences: A331714 A331715 A331716 * A331718 A331719 A331720

Keyword

nonn,more

Author

Andrew Howroyd, Feb 02 2020

Status

approved