A117705 Numbers n such that 5^n-n^5 is prime.

2, 14, 26, 4646, 68484

Offset: 1

Author

Mohammed Bouayoun (Mohammed.Bouayoun(AT)sanef.com), Apr 13 2006, Jan 08 2008

Keywords

• hard
• more
• nonn

Examples

			a(1)=2 because 2^5 - 5^2 = 7 is prime
		

Links

• Henri & Renaud Lifchitz, PRP Records.

Programs

Mathematica

Do[If[PrimeQ[(5^n-n^5)],Print[n]],{n,1,5000}]

PARI

is(n)=isprime(5^n-n^5) \\ Charles R Greathouse IV, Feb 17 2017

Extensions

a(5) found by Donovan Johnson

First five terms confirmed by Dmitry Kamenetsky, Dec 18 2008