A211070 Number of 2 X 2 matrices having all terms in {1,...,n} and determinant d satisfying -n < d < n.

1, 10, 43, 118, 263, 474, 831, 1258, 1893, 2652, 3685, 4748, 6375, 7918, 9931, 12216, 15015, 17654, 21395, 24726, 29253, 33822, 39011, 43906, 50995, 57210, 64431, 71968, 81075, 88962, 100159, 109346, 121107, 132636, 145097

Offset: 1

Author

Clark Kimberling, Mar 31 2012

Keywords

• nonn

Comments

For a guide to related sequences, see A210000.

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, -n, m}]
Table[c1[n, n - 1] - c1[n, -n], {n, 1, z1}] (* A211070 *)