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A211151 Number of 2 X 2 matrices having all terms in {-n,...,0,...,n} and determinant > n.

%I A211151 #12 Jan 14 2017 10:29:03
%S A211151 24,196,784,2304,5324,10964,19756,33772,53496,81396,118452,168324,
%T A211151 229964,310132,407964,527644,670888,844896,1045916,1286220,1560508,
%U A211151 1879548,2244404,2664180,3130076,3663856,4260240,4927920,5665992
%N A211151 Number of 2 X 2 matrices having all terms in {-n,...,0,...,n} and determinant > n.
%C A211151 For a guide to related sequences, see A210000.
%t A211151 a = -n; b = n; z1 = 30;
%t A211151 t[n_] := t[n] = Flatten[Table[w*z - x*y, {w, a, b}, {x, a, b}, {y, a, b}, {z, a, b}]]
%t A211151 c[n_, k_] := c[n, k] = Count[t[n], k]
%t A211151 c1[n_, m_] := c1[n, m] = Sum[c[n, k], {k, -2*n^2, m}]
%t A211151 Table[c1[n,2*n^2]-c1[n,n-1],{n,1,z1}] (*A211151*)
%t A211151 %/4  (* integers *)
%Y A211151 Cf. A210000.
%K A211151 nonn
%O A211151 1,1
%A A211151 _Clark Kimberling_, Apr 04 2012