A211424 Number of ordered triples (w,x,y) with all terms in {-n,...,0,...,n} and w^2+3*x*y=0.

1, 5, 9, 21, 25, 29, 49, 53, 57, 69, 73, 77, 105, 109, 113, 125, 137, 141, 161, 165, 169, 181, 185, 189, 217, 229, 233, 261, 265, 269, 297, 301, 313, 325, 329, 333, 369, 373, 377, 389, 393, 397, 417, 421, 425, 445, 449, 453, 497, 517, 529, 541, 545

Offset: 0

Author

Clark Kimberling, Apr 10 2012

Keywords

• nonn

Comments

For a guide to related sequences, see A211422.

Links

• Brandon Crofts, Table of n, a(n) for n = 0..20000
• Brandon Crofts, Faster Mathematica code for A211424

Crossrefs

Cf. A211422.

Programs

Mathematica

t[n_] := t[n] = Flatten[Table[w^2 + 3 x*y, {w, -n, n}, {x, -n, n}, {y, -n, n}]]
c[n_] := Count[t[n], 0]
t = Table[c[n], {n, 0, 70}]  (* A211424 *)
(t - 1)/4                    (* integers  *)