A212061 Number of (w,x,y,z) with all terms in {1,...,n} and w*x=(y*z)^2.

0, 1, 3, 5, 12, 14, 18, 20, 30, 45, 49, 51, 65, 67, 71, 75, 106, 108, 134, 136, 150, 154, 158, 160, 180, 215, 219, 241, 255, 257, 265, 267, 307, 311, 315, 319, 392, 394, 398, 402, 422, 424, 432, 434, 448, 478, 482, 484, 540, 599, 657, 661, 675, 677

Offset

0,3

Comments

For a guide to related sequences, see A211795.

Links

Table of n, a(n) for n=0..53.

Mathematica

t = Compile[{{n, _Integer}}, Module[{s = 0},
(Do[If[w*x == (y*z)^2, s = s + 1],
{w, 1, #}, {x, 1, #}, {y, 1, #}, {z, 1, #}] &[n]; s)]];
Map[t[#] &, Range[0, 50]] (* A212061 *)
(* Peter J. C. Moses, Apr 13 2012 *)

Crossrefs

Cf. A211795.

Sequence in context: A037221 A182537 A259309 * A287570 A265220 A080560

Adjacent sequences: A212058 A212059 A212060 * A212062 A212063 A212064

Keyword

nonn

Author

Clark Kimberling, Apr 30 2012

Status

approved