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A212102 Number of (w,x,y,z) with all terms in {1,...,n} and 1/w=1/x+1/y+1/z. 2
0, 0, 0, 1, 4, 4, 11, 11, 14, 15, 18, 18, 34, 34, 34, 56, 59, 59, 78, 78, 105, 112, 112, 112, 143, 143, 143, 144, 177, 177, 235, 235, 238, 245, 245, 269, 318, 318, 318, 319, 367, 367, 416, 416, 422, 471, 471, 471, 517, 517, 520, 521, 530, 530, 549, 561 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,5
COMMENTS
For a guide to related sequences, see A211795.
LINKS
EXAMPLE
a(4) counts these: (1,3,3,3), (1,2,4,4), (1,4,2,4), (1,4,4,2).
MATHEMATICA
t = Compile[{{n, _Integer}}, Module[{s = 0},
(Do[If[w*(y*z + z*x + x*y) == x*y*z, s = s + 1],
{w, 1, #}, {x, 1, #}, {y, 1, #}, {z, 1, #}] &[n]; s)]];
Map[t[#] &, Range[0, 60]] (* A212102 *)
(* Peter J. C. Moses, Apr 13 2012 *)
CROSSREFS
Cf. A211795.
Sequence in context: A161433 A180498 A107856 * A168373 A266438 A128499
KEYWORD
nonn
AUTHOR
Clark Kimberling, May 03 2012
STATUS
approved

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Last modified July 22 13:05 EDT 2024. Contains 374499 sequences. (Running on oeis4.)