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A211152
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Number of 2 X 2 matrices having all terms in {-n,...,0,...,n} and determinant >= 2n.
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2
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4, 80, 428, 1428, 3604, 7924, 14988, 26244, 43072, 66844, 98804, 142652, 197584, 268800, 357608, 465888, 596964, 756036, 942160, 1163608, 1420248, 1717344, 2056952, 2451248, 2891420, 3392528, 3958576
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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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MATHEMATICA
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a = -n; b = n; z1 = 27;
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, 2n-1], {n, 1, z1}] (* A211152 *)
%/4 (* integers *)
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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