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A211153 Number of 2 X 2 matrices having all terms in {-n,...,0,..,n} and determinant >= 3n.

%I A211153 #6 Jan 12 2017 01:26:57
%S A211153 0,20,184,804,2284,5408,10780,20084,33664,53840,81124,119156,167872,
%T A211153 231096,309816,409128,527088,673112,842776,1049352,1285760,1561932,
%U A211153 1879908,2247884,2662000,3134360,3662256,4264796,4926892,5673180
%N A211153 Number of 2 X 2 matrices having all terms in {-n,...,0,..,n} and determinant >= 3n.
%C A211153 For a guide to related sequences, see A210000.
%t A211153 a = -n; b = n; z1 = 30;
%t A211153 t[n_] := t[n] = Flatten[Table[w*z - x*y, {w, a, b}, {x, a, b}, {y, a, b}, {z, a, b}]]
%t A211153 c[n_, k_] := c[n, k] = Count[t[n], k]
%t A211153 c1[n_, m_] := c1[n, m] = Sum[c[n, k], {k, -2*n^2, m}]
%t A211153 Table[c1[n,2*n^2]-c1[n,3n-1],{n,1,z1}] (* A211153 *)
%t A211153 %/4 (* integers *)
%Y A211153 Cf. A210000.
%K A211153 nonn
%O A211153 1,2
%A A211153 _Clark Kimberling_, Apr 05 2012