Search: id:A161749
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%I A161749
%S A161749 3,2,7,5,127,3299,1967249047,8191,30450469261
%N A161749 Smallest distinct primes, if they exist, in x^n - y^(n-2).
%C A161749 For even n > 4 = 2m, x^2m - y^(2m-2) = (x^m)^2 - y^((m-1))^2 is divisible 
               by
%C A161749 x^m - y^(m-1) which is not prime. This accounts for the phrase "if they 
               exist"
%C A161749 in the definition.
%o A161749 (PARI) diffpowers(n,m) =
%o A161749 {
%o A161749 local(a,c=0,c2=0,j,k,y);
%o A161749 a=vector(floor(n^2/log(n^2)));
%o A161749 for(j=1,n,
%o A161749 for(k=1,n,
%o A161749 y=j^m-k^(m-1);
%o A161749 if(ispseudoprime(y),
%o A161749 c++;
%o A161749 \\ print(j","k","y);
%o A161749 a[c]=y;
%o A161749 );
%o A161749 );
%o A161749 );
%o A161749 a=vecsort(a);
%o A161749 for(j=2,length(a),
%o A161749 if(a[j]!=a[j-1]&&a[j]!=0,
%o A161749 c2++;
%o A161749 print1(a[j]",");
%o A161749 if(c2>100,break);
%o A161749 );
%o A161749 );
%o A161749 }
%Y A161749 Sequence in context: A155046 A033318 A093780 this_sequence A101307 A096899 
               A154448
%Y A161749 Adjacent sequences: A161746 A161747 A161748 this_sequence A161750 A161751 
               A161752
%K A161749 nonn,uned
%O A161749 1,1
%A A161749 Cino Hilliard (hillcino368(AT)hotmail.com), Jun 17 2009

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