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A212240
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Number of 2 X 2 matrices M of with all terms in {1,...,n} and permanent(M) >= n.
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2
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0, 1, 16, 80, 251, 612, 1269, 2354, 4021, 6449, 9844, 14427, 20458, 28203, 37972, 50073, 64876, 82725, 104046, 129222, 158741, 193024, 232607, 277956, 329675, 388248, 454353, 528508, 611435, 703712, 806121, 919242, 1043953, 1180865
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OFFSET
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0,3
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COMMENTS
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For a guide to related sequences, see A211795.
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LINKS
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FORMULA
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MATHEMATICA
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t = Compile[{{n, _Integer}}, Module[{s = 0},
(Do[If[w*x + y*z >= n, s = s + 1],
{w, 1, #}, {x, 1, #}, {y, 1, #}, {z, 1, #}] &[n]; s)]];
Map[t[#] &, Range[0, 40]] (* A212240 *)
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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