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A211150
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Number of 2x2 matrices having all terms in {-n,...,0,..,n} and determinant > n.
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2
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4, 104, 608, 1940, 4916, 10084, 19052, 32352, 52084, 79308, 116900, 164564, 227860, 306324, 403868, 522256, 667488, 837236, 1041708, 1277060, 1553116, 1871084, 2238452, 2648836, 3121648, 3652200, 4248656, 4911312, 5656784
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OFFSET
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1,1
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COMMENTS
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For a guide to related sequences, see A210000.
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LINKS
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Table of n, a(n) for n=1..29.
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MATHEMATICA
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a = -n; b = n; z1 = 30;
t[n_] := t[n] = Flatten[Table[w*z - x*y, {w, a, b}, {x, a, b}, {y, a, b}, {z, a, b}]]
c[n_, k_] := c[n, k] = Count[t[n], k]
c1[n_, m_] := c1[n, m] = Sum[c[n, k], {k, -2*n^2, m}]
Table[c1[n, 2*n^2] - c1[n, n], {n, 1, z1}] (* A211150 *)
%/4 (* integers *)
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CROSSREFS
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Cf. A210000.
Sequence in context: A091330 A024056 A102439 * A006415 A181396 A196979
Adjacent sequences: A211147 A211148 A211149 * A211151 A211152 A211153
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KEYWORD
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nonn
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AUTHOR
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Clark Kimberling, Apr 04 2012
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STATUS
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approved
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