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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
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-François Alcover, Nov 26 2013 *)
CROSSREFS
Sequence in context: A214908 A143553 A341493 * A363706 A259125 A067056
KEYWORD
nonn,nice,easy
AUTHOR
Vladeta Jovovic, Sep 25 2001
STATUS
approved

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Last modified July 25 14:52 EDT 2024. Contains 374611 sequences. (Running on oeis4.)