A212102 Number of (w,x,y,z) with all terms in {1,...,n} and 1/w=1/x+1/y+1/z.

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

Offset

0,5

Comments

For a guide to related sequences, see A211795.

Links

Seiichi Manyama, Table of n, a(n) for n = 0..150

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

Adjacent sequences: A212099 A212100 A212101 * A212103 A212104 A212105

Keyword

nonn

Author

Clark Kimberling, May 03 2012

Status

approved