OFFSET
0,2
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
KEYWORD
nonn,nice,easy
AUTHOR
Vladeta Jovovic, Sep 25 2001
STATUS
approved