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A064276 Number of 2 X 2 singular integer matrices with elements from {0,...,n} up to row and column permutation. 2
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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified February 1 19:27 EST 2023. Contains 359995 sequences. (Running on oeis4.)