A181491 Primes of the form p = 3*2^k - 1 such that p+2 is also prime.

5, 11, 191, 786431

Offset: 1

Author

M. F. Hasler, Oct 30 2010

Keywords

• bref
• nonn

Comments

Sequence A181490 lists the exponents k, sequences A181492 and A181493 the corresponding upper twin prime and their average.

a(5) > 3 * 2 ^ 3000 + 1. - Max Z. Scialabba, Dec 24 2023

Crossrefs

Cf. A001097, A001359, A006512, A014574.

Programs

PARI

for( k=1,999, ispseudoprime(3<
				

Formula

A181491 = A007283 intersect A014574 = A181492 - 2 = A181493 - 1 = 3*2^A153890 - 1.