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%I #23 Aug 18 2024 20:10:49
%S 5,7,47
%N Primes p such that 5^p - 4 is also prime.
%C If it exists, a(4) > 48091. - _J.W.L. (Jan) Eerland_, Nov 13 2022
%C If it exists, a(4) > 2*10^5 (cf. comment by _Tyler NeSmith_ in A059613). - _Michael S. Branicky_, Aug 17 2024
%F A000040 INTERSECT A059613. - _R. J. Mathar_, Apr 15 2010
%e For p=5, 5^5-4=3121; p=7, 5^7-4=78121; p=47, 5^47-4= 710542735760100185871124267578121
%o (Magma) [p: p in PrimesUpTo(3500) | IsPrime(5^p-4)];
%o (PARI) is(n)=isprime(n) && isprime(5^n-4) \\ _Charles R Greathouse IV_, Sep 06 2016
%Y Cf. A000040, A059613.
%K nonn,more,bref
%O 1,1
%A _Vincenzo Librandi_, Mar 14 2010