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A211060
Number of 2 X 2 matrices having all terms in {1,...,n} and determinant >n.
3
0, 1, 12, 53, 158, 361, 740, 1326, 2235, 3524, 5361, 7711, 10926, 14941, 20011, 26217, 33964, 43007, 54094, 66834, 81956, 99455, 119872, 142543, 169036, 198791, 232419, 269781, 312224, 358359, 410670, 467577, 530755, 599962, 676006
OFFSET
1,3
COMMENTS
For a guide to related sequences, see A210000.
MATHEMATICA
a = 1; b = n; z1 = 40;
t[n_] := t[n] = Flatten[Table[w*z - x*y, {w, a, b}, {x, a, b}, {y, a, b}, {z, a, b}]]
c[n_, k_] := c[n, k] = Count[t[n], k]
c1[n_, m_] := c1[n, m] = Sum[c[n, k], {k, 0, m}]
Table[c1[n, n^2] - c1[n, n], {n, 1, z1}]
CROSSREFS
Cf. A210000.
Sequence in context: A268186 A253130 A213549 * A242514 A030182 A060171
KEYWORD
nonn
AUTHOR
Clark Kimberling, Mar 31 2012
STATUS
approved