A064276 - OEIS

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

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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