A211425 Number of ordered triples (w,x,y) with all terms in {-n,...,0,...,n} and w^2+4*x*y=0.

1, 5, 13, 17, 33, 37, 45, 49, 65, 77, 85, 89, 113, 117, 125, 129, 153, 157, 173, 177, 193, 197, 205, 209, 241, 261, 269, 281, 297, 301, 317, 321, 345, 349, 357, 361, 401, 405, 413, 417, 441, 445, 453, 457, 473, 485, 493, 497, 537, 565, 589, 593, 609

Offset

0,2

Comments

For a guide to related sequences, see A211422.

Links

Table of n, a(n) for n=0..52.

Mathematica

t[n_] := t[n] = Flatten[Table[w^2 + 4 x*y, {w, -n, n}, {x, -n, n}, {y, -n, n}]]
c[n_] := Count[t[n], 0]
t = Table[c[n], {n, 0, 70}]  (* A211425 *)
(t - 1)/4                    (* integers *)

Crossrefs

Cf. A211422.

Sequence in context: A038938 A253079 A184851 * A245906 A191108 A216575

Adjacent sequences: A211422 A211423 A211424 * A211426 A211427 A211428

Keyword

nonn

Author

Clark Kimberling, Apr 10 2012

Status

approved