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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.
2

%I #5 Feb 07 2020 20:49:28

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

%N 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.

%e The a(3) = 4 matrices are:

%e [1 1 1] [1 1 0] [1 1 1] [1 1 0]

%e [1 0 0] [1 0 1] [1 1 0] [1 0 1]

%e [0 1 0] [0 1 0] [0 0 1] [0 1 1]

%e [0 0 1] [0 0 1]

%Y Row n=2 of A331510.

%Y Cf. A331718.

%K nonn,more

%O 0,4

%A _Andrew Howroyd_, Feb 02 2020