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A211152 Number of 2 X 2 matrices having all terms in {-n,...,0,...,n} and determinant >= 2n.

%I A211152 #7 Jan 12 2017 01:56:32
%S A211152 4,80,428,1428,3604,7924,14988,26244,43072,66844,98804,142652,197584,
%T A211152 268800,357608,465888,596964,756036,942160,1163608,1420248,1717344,
%U A211152 2056952,2451248,2891420,3392528,3958576
%N A211152 Number of 2 X 2 matrices having all terms in {-n,...,0,...,n} and determinant >= 2n.
%C A211152 For a guide to related sequences, see A210000.
%t A211152 a = -n; b = n; z1 = 27;
%t A211152 t[n_] := t[n] = Flatten[Table[w*z - x*y, {w, a, b}, {x, a, b}, {y, a, b}, {z, a, b}]]
%t A211152 c[n_, k_] := c[n, k] = Count[t[n], k]
%t A211152 c1[n_, m_] := c1[n, m] = Sum[c[n, k], {k, -2*n^2, m}]
%t A211152 Table[c1[n,2*n^2]-c1[n,2n-1],{n,1,z1}] (* A211152 *)
%t A211152 %/4  (* integers *)
%Y A211152 Cf. A210000.
%K A211152 nonn
%O A211152 1,1
%A A211152 _Clark Kimberling_, Apr 05 2012