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A212741
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Number of (w,x,y,z) with all terms in {0,...,n} and max{w,x,y,z}>=2*min{w,x,y,z}.
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3
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1, 15, 79, 239, 593, 1199, 2239, 3759, 6049, 9119, 13391, 18815, 25969, 34719, 45823, 59039, 75329, 94319, 117199, 143439, 174481, 209615, 250559, 296399, 349153, 407679, 474319, 547679, 630449, 720959, 822271, 932415, 1054849
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OFFSET
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0,2
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COMMENTS
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Also the number of (w,x,y,z) with all terms in {0,...,n} and at least one term <= range{w,x,y,z}.
Every term is odd.
For a guide to related sequences, see A211795.
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LINKS
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FORMULA
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a(n) = 2*a(n-1)+2*a(n-2)-6*a(n-3)+6*a(n-5)-2*a(n-6)-2*a(n-7)+a(n-8).
G.f.: ( -1-13*x-47*x^2-57*x^3-47*x^4-3*x^5-x^6+x^7 ) / ( (1+x)^3*(x-1)^5 ).
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MATHEMATICA
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t = Compile[{{n, _Integer}}, Module[{s = 0},
(Do[If[Max[w, x, y, z] >= 2 Min[w, x, y, z], s = s + 1],
{w, 0, n}, {x, 0, n}, {y, 0, n}, {z, 0, n}]; s)]];
Map[t[#] &, Range[0, 40]] (* A212741 *)
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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