cp's OEIS Frontend

A161747 Primes of the form x^5-y^4, where x,y >= 1.

%I A161747 #5 Oct 01 2013 21:35:30
%S A161747 31,227,1051,3109,7151,15511,18127,30367,32143,32687,144719,151051,
%T A161747 165311,186343,234191,302399,369997,371281,374239,407503,454303,
%U A161747 509263,531263,537743,759359,1053007,1088081,1182287,1185601,1354321,1381441
%N A161747 Primes of the form x^5-y^4, where x,y >= 1.
%C A161747 If a prime has multiple representations of the format, it is entered only once.
%F A161747 If x^5-y^4 is prime for integers x,y list without duplicates.
%e A161747 2^5 - 1^4 = 31.
%o A161747 (PARI) diffpowers(n,m) =
%o A161747 {
%o A161747 local(a,c=0,c2=0,j,k,y);
%o A161747 a=vector(floor(n^2/log(n^2)));
%o A161747 for(j=1,n,
%o A161747 for(k=1,n,
%o A161747 y=j^m-k^(m-1);
%o A161747 if(ispseudoprime(y),
%o A161747 c++;
%o A161747 \\ print(j","k","y);
%o A161747 a[c]=y;
%o A161747 );
%o A161747 );
%o A161747 );
%o A161747 a=vecsort(a);
%o A161747 for(j=2,length(a),
%o A161747 if(a[j]!=a[j-1]&&a[j]!=0,
%o A161747 c2++;
%o A161747 print1(a[j]",");
%o A161747 if(c2>100,break);
%o A161747 );
%o A161747 );
%o A161747 }
%K A161747 nonn
%O A161747 1,1
%A A161747 _Cino Hilliard_, Jun 17 2009