A359630 Primes p such that 10^p+3 or 10^p+9 is also prime.

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

Offset: 1

Author

Mikk Heidemaa, Jan 08 2023

Keywords

• nonn
• base
• hard
• more

Comments

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

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

Examples

			3 is a term since it is prime and so is 10^3 + 9 = 1009.
11 is a term since it is prime and 10^11 + 3 = 100000000003 is also a prime.
		

Crossrefs

Cf. A049054, A088275.

Programs

Mathematica

Block[{p}, ParallelDo[p := Prime @ i; If[(PrimeQ[10^p + 3] || PrimeQ[10^p + 9]), Print @ p], {i, PrimePi @ 48109}, Method -> "FinestGrained"]]
Select[Prime[Range[5000]],AnyTrue[10^#+{3,9},PrimeQ]&] (* Harvey P. Dale, Feb 09 2025 *)