A295111 Primes p such that 2^p - p is also a prime.

2, 3, 13, 19, 481801

Offset: 1

Author

Iain Fox, Nov 14 2017

Keywords

• hard
• more
• nonn

Comments

a(6) > 1061095.

Intersection of A000040 and A048744.

Since numbers other than 3 that are congruent to 3 mod 6 are composite, for n > 2, a(n) is congruent to 1 mod 6 (see comments by Iain Fox in A048744).

Examples

			p=13, 2^13 - 13 = 8179 is prime.
		

Crossrefs

Cf. A000325, A081296, A048744, A057663, A057673.

Programs

PARI

lista(nn) = forprime(p=2, nn, if(ispseudoprime(2^p - p), print1(p, ", ")))