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

2, 14, 26, 4646, 68484

Offset

1,1

Links

Table of n, a(n) for n=1..5.

Henri & Renaud Lifchitz, PRP Records.

Example

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

Mathematica

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

Prog

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

Crossrefs

Sequence in context: A032461 A072390 A213136 * A330789 A031079 A364764

Adjacent sequences: A117702 A117703 A117704 * A117706 A117707 A117708

Keyword

hard,more,nonn

Author

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

Extensions

a(5) found by Donovan Johnson

First five terms confirmed by Dmitry Kamenetsky, Dec 18 2008

Status

approved