A211069 Number of 2 X 2 matrices having all terms in {1,...,n} and determinant in [-n,n].

1, 14, 57, 150, 309, 574, 921, 1444, 2091, 2952, 3919, 5314, 6709, 8534, 10603, 13102, 15593, 18962, 22133, 26332, 30569, 35346, 40097, 46690, 52553, 59394, 66603, 75094, 82833, 93282, 102181, 113422, 124411, 136412, 148613

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], {n, 1, z1}]  (* A211069 *)