A211515 Number of ordered triples (w,x,y) with all terms in {1,...,n} and w^3=x*y.

0, 1, 1, 1, 3, 3, 3, 3, 6, 8, 8, 8, 8, 8, 8, 8, 10, 10, 12, 12, 12, 12, 12, 12, 14, 16, 16, 21, 21, 21, 21, 21, 25, 25, 25, 25, 27, 27, 27, 27, 29, 29, 29, 29, 29, 29, 29, 29, 31, 33, 35, 35, 35, 35, 39, 39, 41, 41, 41, 41, 41, 41, 41, 41, 48, 48, 48, 48, 48, 48, 48

Offset: 0

Author

Clark Kimberling, Apr 14 2012

Keywords

• nonn

Comments

For a guide to related sequences, see A211422.

Crossrefs

Cf. A211422, A010057.

Programs

Mathematica

t[n_] := t[n] = Flatten[Table[w^3 - x*y, {w, 1, n}, {x, 1, n}, {y, 1, n}]]
c[n_] := Count[t[n], 0]
t = Table[c[n], {n, 0, 70}]  (* A211515 *)

Formula

a(n) = Sum_{i=1..n} Sum_{j=1..n} A010057(i*j). - Ridouane Oudra, Oct 17 2020