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

%I A211150 #7 Jan 12 2017 01:55:12
%S A211150 4,104,608,1940,4916,10084,19052,32352,52084,79308,116900,164564,
%T A211150 227860,306324,403868,522256,667488,837236,1041708,1277060,1553116,
%U A211150 1871084,2238452,2648836,3121648,3652200,4248656,4911312,5656784
%N A211150 Number of 2 X 2 matrices having all terms in {-n,...,0,...,n} and determinant > n.
%C A211150 For a guide to related sequences, see A210000.
%t A211150 a = -n; b = n; z1 = 30;
%t A211150 t[n_] := t[n] = Flatten[Table[w*z - x*y, {w, a, b}, {x, a, b}, {y, a, b}, {z, a, b}]]
%t A211150 c[n_, k_] := c[n, k] = Count[t[n], k]
%t A211150 c1[n_, m_] := c1[n, m] = Sum[c[n, k], {k, -2*n^2, m}]
%t A211150 Table[c1[n, 2*n^2] - c1[n, n], {n, 1, z1}]  (* A211150 *)
%t A211150 %/4  (* integers *)
%Y A211150 Cf. A210000.
%K A211150 nonn
%O A211150 1,1
%A A211150 _Clark Kimberling_, Apr 04 2012