A211070 - OEIS

%I #6 Jan 14 2017 01:37:38

%S 1,10,43,118,263,474,831,1258,1893,2652,3685,4748,6375,7918,9931,

%T 12216,15015,17654,21395,24726,29253,33822,39011,43906,50995,57210,

%U 64431,71968,81075,88962,100159,109346,121107,132636,145097

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

%C For a guide to related sequences, see A210000.

%t a = 1; b = n; z1 = 35;

%t t[n_] := t[n] = Flatten[Table[w*z - x*y, {w, a, b}, {x, a, b}, {y, a, b}, {z, a, b}]]

%t c[n_, k_] := c[n, k] = Count[t[n], k]

%t c1[n_, m_] := c1[n, m] = Sum[c[n, k], {k, -n, m}]

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

%Y Cf. A210000.

%K nonn

%O 1,2

%A _Clark Kimberling_, Mar 31 2012