A135782 Positive numbers of the form 3*x*y^2 - x^3 (where x,y are positive integers).

2, 9, 10, 11, 16, 26, 36, 38, 44, 46, 47, 54, 72, 74, 80, 88, 107, 115, 117, 128, 135, 142, 146, 182, 187, 191, 198, 208, 234, 236, 242, 243, 250, 270, 286, 288, 297, 299, 304, 341, 352, 362, 368, 376, 413, 414, 415, 431, 432, 470, 478, 504, 506, 524, 530, 549

Offset

1,1

Links

Robert Israel, Table of n, a(n) for n = 1..10000

Maple

N:= 10^4: # for terms <= N
S:= {}:
for x from 1 to floor(N/2) do
  S:= S union {seq(3*x*y^2 - x^3, y = ceil(x/sqrt(3)) .. floor(sqrt((x^2+N/x)/3)))}
od:
sort(convert(S, list)); # Robert Israel, Aug 14 2023

Mathematica

a = {}; Do[Do[w = 3x y^2 - x^3; If[(w > 0) && w < 3000, AppendTo[a, w]], {x, 1, 1000}], {y, 1, 1000}]; Union[a]

Crossrefs

Cf. A135781, A364974.

Sequence in context: A043065 A077214 A167451 * A281899 A037457 A037314

Adjacent sequences: A135779 A135780 A135781 * A135783 A135784 A135785

Keyword

nonn

Author

Artur Jasinski, Nov 29 2007

Status

approved