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

0,2

Links

Table of n, a(n) for n=0..46.

Formula

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

Example

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.

Sequence in context: A147205 A146875 A241233 * A240001 A301685 A102724

Adjacent sequences: A064273 A064274 A064275 * A064277 A064278 A064279

Keyword

nonn

Author

Vladeta Jovovic, Sep 24 2001

Extensions

More terms from David Wasserman, Jul 16 2002

Status

approved