A211150 Number of 2 X 2 matrices having all terms in {-n,...,0,...,n} and determinant > n.

4, 104, 608, 1940, 4916, 10084, 19052, 32352, 52084, 79308, 116900, 164564, 227860, 306324, 403868, 522256, 667488, 837236, 1041708, 1277060, 1553116, 1871084, 2238452, 2648836, 3121648, 3652200, 4248656, 4911312, 5656784

Offset

1,1

Comments

For a guide to related sequences, see A210000.

Links

Table of n, a(n) for n=1..29.

Mathematica

a = -n; b = n; z1 = 30;
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, -2*n^2, m}]
Table[c1[n, 2*n^2] - c1[n, n], {n, 1, z1}]  (* A211150 *)
%/4  (* integers *)

Crossrefs

Cf. A210000.

Sequence in context: A300976 A102439 A331456 * A281534 A006415 A333434

Adjacent sequences: A211147 A211148 A211149 * A211151 A211152 A211153

Keyword

nonn

Author

Clark Kimberling, Apr 04 2012

Status

approved