login
A135782
Positive numbers of the form 3*x*y^2 - x^3 (where x,y are positive integers).
3
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
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]
With[{nn=300}, Select[Flatten[Table[3*x*y^2-x^3, {x, nn}, {y, nn}]], 0<#<600&]//Union] (* Harvey P. Dale, Jul 03 2024 *)
CROSSREFS
Sequence in context: A077214 A378073 A167451 * A281899 A037457 A037314
KEYWORD
nonn
AUTHOR
Artur Jasinski, Nov 29 2007
STATUS
approved