A064276 Number of 2 X 2 singular integer matrices with elements from {0,...,n} up to row and column permutation.

1, 5, 13, 25, 42, 62, 90, 118, 155, 195, 243, 287, 352, 404, 472, 548, 629, 697, 797, 873, 986, 1094, 1202, 1294, 1443, 1559, 1687, 1823, 1984, 2100, 2296, 2420, 2597, 2769, 2937, 3125, 3366, 3514, 3702, 3906, 4167, 4331, 4611, 4783, 5040, 5320, 5548

Offset: 0

Author

Vladeta Jovovic, Sep 24 2001

Keywords

• nonn

Examples

			There are 5 binary singular matrices up to row and column permutation:
[0 0] [1 0] [1 1] [1 0] [1 1]
[0 0] [0 0] [0 0] [1 0] [1 1].
		

Crossrefs

Cf. A059306, A062801, A059976.

Formula

a(n) = (A059306(n)+(n+1)*(2*n+3))/4.

Extensions

More terms from David Wasserman, Jul 16 2002