A174267 Primes p such that 5^p - 4 is also prime.

5, 7, 47

Offset

1,1

Comments

If it exists, a(4) > 48091. - J.W.L. (Jan) Eerland, Nov 13 2022

If it exists, a(4) > 2*10^5 (cf. comment by Tyler NeSmith in A059613). - Michael S. Branicky, Aug 17 2024

Links

Table of n, a(n) for n=1..3.

Formula

A000040 INTERSECT A059613. - R. J. Mathar, Apr 15 2010

Example

For p=5, 5^5-4=3121; p=7, 5^7-4=78121; p=47, 5^47-4= 710542735760100185871124267578121

Prog

(Magma) [p: p in PrimesUpTo(3500) | IsPrime(5^p-4)];
(PARI) is(n)=isprime(n) && isprime(5^n-4) \\ Charles R Greathouse IV, Sep 06 2016

Crossrefs

Cf. A000040, A059613.

Sequence in context: A090520 A066219 A278618 * A306649 A075830 A058313

Adjacent sequences: A174264 A174265 A174266 * A174268 A174269 A174270

Keyword

nonn,more,bref

Author

Vincenzo Librandi, Mar 14 2010

Status

approved