A211507 Number of ordered triples (w,x,y) with all terms in {1,...,n} and w^2=x*y-n.

0, 0, 0, 1, 2, 3, 4, 3, 9, 9, 4, 17, 11, 7, 18, 16, 19, 21, 16, 21, 35, 24, 8, 35, 42, 17, 44, 40, 25, 47, 28, 47, 56, 28, 30, 76, 69, 11, 52, 68, 54, 81, 36, 33, 99, 61, 38, 99, 77, 51, 76, 88, 63, 67, 92, 88, 140, 40, 12, 153, 90, 71, 98, 121, 98, 104, 100, 41

Offset: 0

Author

Clark Kimberling, Apr 14 2012

Keywords

• nonn

Comments

For a guide to related sequences, see A211422.

Crossrefs

Cf. A211422.

Programs

Mathematica

t[n_] := t[n] = Flatten[Table[w^2 - x*y + n, {w, 1, n}, {x, 1, n}, {y, 1, n}]]
c[n_] := Count[t[n], 0]
t = Table[c[n], {n, 0, 80}]  (* A211507 *)