login

Reminder: The OEIS is hiring a new managing editor, and the application deadline is January 26.

Primes p such that 10^p+3 or 10^p+9 is also prime.
0

%I #41 Feb 24 2023 16:58:03

%S 2,3,5,11,17,101,107,26927,48109

%N Primes p such that 10^p+3 or 10^p+9 is also prime.

%C Union of the terms which are prime in A049054 and in A088275.

%C If it exists, a(10) > 2*10^5 (according to the comment at A088275).

%e 3 is a term since it is prime and so is 10^3 + 9 = 1009.

%e 11 is a term since it is prime and 10^11 + 3 = 100000000003 is also a prime.

%t Block[{p}, ParallelDo[p := Prime @ i; If[(PrimeQ[10^p + 3] || PrimeQ[10^p + 9]), Print @ p], {i, PrimePi @ 48109}, Method -> "FinestGrained"]]

%Y Cf. A049054, A088275.

%K nonn,base,hard,more

%O 1,1

%A _Mikk Heidemaa_, Jan 08 2023