A211061 Number of 2 X 2 matrices having all terms in {1,...,n} and determinant >= n.

0, 3, 19, 69, 181, 411, 785, 1419, 2334, 3674, 5478, 7994, 11093, 15249, 20347, 26660, 34253, 43661, 54463, 67637, 82614, 100217, 120415, 143935, 169815, 199883, 233505, 271344, 313103, 360519, 411681, 469615, 532407, 601850, 677764

Offset: 1

Author

Clark Kimberling, Mar 31 2012

Keywords

• nonn

Comments

For a guide to related sequences, see A210000.

Links

• Chai Wah Wu, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A210000.

Programs

Mathematica

a = 1; b = n; z1 = 35;
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 - 1], {n, 1, z1}]