OFFSET
1,1
COMMENTS
For primes p, q, r the sum p^4 + q^4 + r^4 can be prime only if at least one of p, q, r equals 3. This sequence is the special case q = 13, r = 3.
It is conjectured that the sequence is infinite.
There are prime twins (11, 13) and other consecutive primes (421, 431; 1823, 1831) in the sequence.
LINKS
Harvey P. Dale, Table of n, a(n) for n = 1..1000
EXAMPLE
p = 3: 3^4 + 13^4 + 3^4 = 28723 is prime, so 3 is in the sequence.
p = 5: 5^4 + 13^4 + 3^4 = 29267 = 7*37*113, so 5 is not in the sequence.
p = 17: 17^4 + 13^4 + 3^4 = 112163 is prime, so 17 is in the sequence.
p = 83: 83^4 + 13^4 + 3^4 = 47486963 is prime, so 83 is in the sequence.
MATHEMATICA
Select[Prime[Range[400]], PrimeQ[#^4+28642]&] (* Harvey P. Dale, Dec 14 2011 *)
PROG
(Magma) [ p: p in PrimesUpTo(1840) | IsPrime(p^4+28642) ]; // Klaus Brockhaus, May 03 2009
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Ulrich Krug (leuchtfeuer37(AT)gmx.de), Apr 30 2009
EXTENSIONS
Edited and extended beyond 857 by Klaus Brockhaus, May 03 2009
STATUS
approved