A211513 Number of ordered triples (w,x,y) with all terms in {1,...,n} and 2*w^2=x*y.

0, 0, 2, 2, 4, 4, 6, 6, 10, 14, 16, 16, 18, 18, 20, 20, 24, 24, 32, 32, 34, 34, 36, 36, 40, 46, 48, 52, 54, 54, 56, 56, 66, 66, 68, 68, 76, 76, 78, 78, 82, 82, 84, 84, 86, 90, 92, 92, 96, 104, 118, 118, 120, 120, 128, 128, 132, 132, 134, 134, 136, 136, 138, 142

Offset

0,3

Comments

For a guide to related sequences, see A211422.

Links

Table of n, a(n) for n=0..63.

Mathematica

t[n_] := t[n] = Flatten[Table[2 w^2 - x*y, {w, 1, n}, {x, 1, n}, {y, 1, n}]]
c[n_] := Count[t[n], 0]
t = Table[c[n], {n, 0, 70}]  (* A211513 *)
t/2                          (* integers *)

Crossrefs

Cf. A211422.

Sequence in context: A357454 A357452 A211511 * A309686 A320008 A127370

Adjacent sequences: A211510 A211511 A211512 * A211514 A211515 A211516

Keyword

nonn

Author

Clark Kimberling, Apr 14 2012

Status

approved