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A213492
Number of (w,x,y) with all terms in {0,...,n} and w != min(|w-x|, |x-y|, |y-w|).
2
0, 4, 18, 48, 98, 178, 290, 442, 640, 890, 1196, 1568, 2008, 2524, 3122, 3808, 4586, 5466, 6450, 7546, 8760, 10098, 11564, 13168, 14912, 16804, 18850, 21056, 23426, 25970, 28690, 31594, 34688, 37978, 41468, 45168, 49080, 53212, 57570
OFFSET
0,2
COMMENTS
Every term is even.
For a guide to related sequences, see A212959.
FORMULA
a(n) = 2*a(n-1) - a(n-3) - a(n-4) + 2*a(n-6) - a(n-7).
G.f.: (2*x*(2 + 5*x + 6*x^2 + 3*x^3 + 2*x^4))/((-1 + x)^4 (1 + x) (1 + x + x^2)).
a(n) = (n+1)^3 - A213495(n).
MATHEMATICA
t = Compile[{{n, _Integer}}, Module[{s = 0},
(Do[If[w != Min[Abs[w - x], Abs[x - y], Abs[y - w]], s = s + 1], {w, 0, n}, {x, 0, n}, {y, 0, n}]; s)]];
m = Map[t[#] &, Range[0, 60]] (* this sequence *)
m/2 (* integers *)
CROSSREFS
Sequence in context: A213926 A023650 A254950 * A163188 A114364 A045991
KEYWORD
nonn,easy
AUTHOR
Clark Kimberling, Jun 14 2012
STATUS
approved