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A064363 Number of 2 X 2 regular integer matrices with elements from {0,...,n} up to row and column permutation. 0
0, 2, 14, 51, 133, 289, 547, 954, 1546, 2380, 3508, 5005, 6915, 9347, 12353, 16028, 20468, 25790, 32054, 39427, 47965, 57833, 69155, 82082, 96682, 113192, 131720, 152429, 175467, 201075, 229305, 260492, 294700, 332182, 373138, 417751, 466201 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Table of n, a(n) for n=0..36.

FORMULA

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

EXAMPLE

There are 2 binary regular matrices up to row and column permutation:

[1 0] [1 1]

[0 1] [1 0].

MATHEMATICA

A059306[0] = 1; A059306[n_] := Table[{w, x, y, z} /. {ToRules[ Reduce[0 <= x <= n && 0 <= y <= n && 0 <= z <= n && w*z - x*y == 0, {x, y, z}, Integers]]}, {w, 0, n}] // Flatten[#, 1] & // Length; a[n_] := ((n + 1)*(n^3 + 3*n^2 + 4*n + 1) - A059306[n])/4; Table[Print[an = a[n]]; an, {n, 0, 36}] (* Jean-Fran├žois Alcover, Nov 26 2013 *)

CROSSREFS

Cf. A064276, A059306, A062801, A059976, A039623.

Sequence in context: A153978 A214908 A143553 * A259125 A067056 A208428

Adjacent sequences:  A064360 A064361 A064362 * A064364 A064365 A064366

KEYWORD

nonn,nice,easy

AUTHOR

Vladeta Jovovic, Sep 25 2001

STATUS

approved

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Last modified March 25 10:22 EDT 2019. Contains 321470 sequences. (Running on oeis4.)