A211062 Number of 2 X 2 matrices having all terms in {1,...,n} and determinant >= 2n.

0, 0, 5, 29, 93, 235, 493, 936, 1622, 2642, 4057, 6055, 8608, 12001, 16297, 21619, 28127, 36170, 45624, 57041, 70350, 85892, 103748, 124748, 148174, 175083, 205683, 239800, 277908, 321224, 368301, 421093, 479209, 543193, 613374

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 = 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]
d[n_, m_] := d[n, m] = Sum[c[n, k], {k, 0, m}]
Table[d[n, n^2] - d[n, 2 n - 1], {n, 1, z1}]