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A213045
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Number of (w,x,y) with all terms in {0,...,n} and 2*|w-x| > max(w,x,y) - min(w,x,y).
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2
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0, 4, 14, 36, 72, 128, 206, 312, 448, 620, 830, 1084, 1384, 1736, 2142, 2608, 3136, 3732, 4398, 5140, 5960, 6864, 7854, 8936, 10112, 11388, 12766, 14252, 15848, 17560, 19390, 21344, 23424, 25636, 27982, 30468, 33096, 35872, 38798, 41880
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OFFSET
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0,2
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COMMENTS
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Every term is even.
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LINKS
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FORMULA
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a(n) = 3*a(n-1) - 2*a(n-2) - 2*a(n-3) + 3*a(n-4) - a(n-5).
G.f.: 2*x*(2 + x + x^2)/((-1 + x)^4*(1 + x)).
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MATHEMATICA
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t = Compile[{{n, _Integer}}, Module[{s = 0}, (Do[If[Max[w, x, y] - Min[w, x, y] < 2 Abs[w - x], s = s + 1], {w, 0, n}, {x, 0, n}, {y, 0, n}]; s)]];
m = Map[t[#] &, Range[0, 45]] (* this sequence *)
m/2 (* integers *)
LinearRecurrence[{3, -2, -2, 3, -1}, {0, 4, 14, 36, 72}, 50] (* Harvey P. Dale, Jul 31 2013 *)
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CROSSREFS
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See A212959 for a guide to related sequences.
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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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