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

31, 227, 1051, 3109, 7151, 15511, 18127, 30367, 32143, 32687, 144719, 151051, 165311, 186343, 234191, 302399, 369997, 371281, 374239, 407503, 454303, 509263, 531263, 537743, 759359, 1053007, 1088081, 1182287, 1185601, 1354321, 1381441

Offset

1,1

Comments

If a prime has multiple representations of the format, it is entered only once.

Links

Table of n, a(n) for n=1..31.

Formula

If x^5-y^4 is prime for integers x,y list without duplicates.

Example

2^5 - 1^4 = 31.

Prog

(PARI) diffpowers(n, m) =
{
local(a, c=0, c2=0, j, k, y);
a=vector(floor(n^2/log(n^2)));
for(j=1, n,
for(k=1, n,
y=j^m-k^(m-1);
if(ispseudoprime(y),
c++;
\\ print(j", "k", "y);
a[c]=y;
);
);
);
a=vecsort(a);
for(j=2, length(a),
if(a[j]!=a[j-1]&&a[j]!=0,
c2++;
print1(a[j]", ");
if(c2>100, break);
);
);
}

Crossrefs

Sequence in context: A075931 A142440 A075932 * A059899 A140846 A082544

Adjacent sequences: A161744 A161745 A161746 * A161748 A161749 A161750

Keyword

nonn

Author

Cino Hilliard, Jun 17 2009

Status

approved