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 A161682 Primes that are not of the form x^3 - y^2. 0

%I

%S 3,5,17,29,31,37,41,43,59,73,97,101,103,113,131,137,149,157,163,173,

%T 179,181,197,211,227,229,241,257,263,269,281,283,311,313,317,331,337,

%U 347,349,353,367,373,379,383,389,397,401,409,419,421,443,449,457,461,467,479,491,509,521,523,541

%N Primes that are not of the form x^3 - y^2.

%C The current values are conjectural as they have been reduced from a finite list of values x^3 - y^2 within a search radius x,y < 10000.

%C Conjecture: The sequence is infinite.

%C No more solutions with x < 2.2*10^9. - _Daniel Starodubtsev_, Jan 22 2020

%F A000040 \ A161681.

%t (* assuming x < 10^4 *) notOfTheForm[p_] := Do[r = Reduce[ y > 0 && p == x^3 - y^2, {y}, Integers]; If[r =!= False, If[x > xmax, xmax = x; Print["xmax = ", xmax]]; Return[True]], {x, 1, 10^4}] =!= True; xmax = 1; Reap[ Do[ If[ notOfTheForm[p], Print["p = ", p]; Sow[p]], {p, Prime /@ Range[100]}]][[2, 1]]] (* _Jean-François Alcover_, Oct 09 2012 *)

%o (PARI) diffcubesq(n) =

%o {

%o local(a,c=0,c2=0,j,k,y);

%o a=vector(floor(n^2/log(n^2)));

%o for(j=1,n,

%o for(k=1,n, y=j^3-k^2; if(ispseudoprime(y), c++; a[c]=y;););

%o );

%o a=vecsort(a);

%o for(j=2,c/2,

%o if(a[j]!=a[j-1], c2++; print1(a[j]","); if(c2>100,break););

%o );

%o }

%K nonn

%O 1,1

%A _Cino Hilliard_, Jun 16 2009

%E Worthless link removed by _R. J. Mathar_, Jul 16 2009

%E a(28)-a(61) from _Jean-François Alcover_, Oct 09 2012

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Last modified January 27 13:45 EST 2022. Contains 350607 sequences. (Running on oeis4.)