cp's OEIS Frontend

A080761 Positive numbers of the form y^2 - x^3, x and y >= 1.

%I A080761 #34 Mar 13 2023 10:21:59
%S A080761 1,3,8,9,12,15,17,18,19,22,24,28,30,35,36,37,38,40,41,44,48,54,55,56,
%T A080761 57,63,64,65,68,71,73,79,80,89,92,94,97,98,99,100,101,105,106,107,108,
%U A080761 112,113,117,119,120,121,128,129,131,132,136,138,141,142,143,145,148,151
%N A080761 Positive numbers of the form y^2 - x^3, x and y >= 1.
%C A080761 From _Artur Jasinski_, Oct 03 2007: (Start)
%C A080761 Some numbers have multiple partitions:
%C A080761   8 = 4^2 - 8^3 = 312^2 - 46^3,
%C A080761   9 = 6^2 - 3^3 = 15^2 - 6 ^3 = 253^2 - 40^3. (End)
%C A080761 This is Mordell's equation with the condition that x and y are positive. Sequence A054504 lists the n for which there is no solution to Mordell's equation. Hence, none of those numbers will be in this sequence. The terms of this sequence can be determined by looking at the link to Gebel's data. - _T. D. Noe_, Mar 23 2011
%H A080761 J. Gebel, <a href="/A001014/a001014.txt">Integer points on Mordell curves</a> [Cached copy, after the original web site tnt.math.se.tmu.ac.jp was shut down in 2017]
%H A080761 J. Gebel, A. Petho and H. G. Zimmer, <a href="http://dx.doi.org/10.1023/A:1000281602647">On Mordell's equation</a>, Compositio Math. 110 (1998), 335-367.
%H A080761 Cino Hilliard, <a href="http://groups.msn.com/BC2LCC/n37ltk2.msnw">Proof that n^3+7 <> k^2 for all integers n,k</a>.
%e A080761 8 is in the sequence since 3^2 = 1^3 + 8.
%t A080761 With[{nn=100},Take[Union[Select[First[#]^2-Last[#]^3&/@Tuples[Range[ 20nn],2],#>0&]],nn]] (* _Harvey P. Dale_, Jul 10 2012 *)
%o A080761 (PARI) diop(n,m) = { for(p=1,m, for(x=1,n, y=x*x*x+p; if(issquare(y),print1(p" "); break) ) ) }
%Y A080761 Complement of A080762.
%Y A080761 Cf. sequences for n^3+7, n^3+17, n^3+3, n^3+2, n^3+5.
%Y A080761 Cf. A029727, A029728, A134042, A134043.
%K A080761 nonn
%O A080761 1,2
%A A080761 _Cino Hilliard_, Mar 10 2003
%E A080761 "Positive" added to definition by _N. J. A. Sloane_, Oct 06 2007