A057665 Numbers k such that prime(k) + 2^prime(k) is prime.

2, 3, 24, 66, 126

Offset: 1

Author

Labos Elemer, Oct 16 2000

Keywords

• nonn
• more
• hard

Comments

a(6) > 3002, since prime(3002) = 27479 (see comment by Ralf Stephan in A057663). - Michel Marcus, Dec 20 2013

These values correspond to indices ip = 2, 3, 9, 10, 11 where A052007(ip) is prime. - Michel Marcus, Dec 20 2013

If it exists, a(6) > 15*10^3. - Michal Paulovic, Sep 24 2023

If it exists, a(6) > 30*10^3. - Michael S. Branicky, Sep 01 2024

Crossrefs

Cf. A052007, A057663, A057664.

Programs

Mathematica

Select[Range[10^3], PrimeQ[# + 2^#] &@ Prime@ # &] (* Michael De Vlieger, Oct 26 2017 *)

PARI

isok(n) = isprime(prime(n) + 2^prime(n)); \\ Michel Marcus, Dec 19 2013

Formula

a(n) = primepi(A057663(n)). - Michel Marcus, Dec 20 2013

Extensions

Name edited by Michel Marcus, Dec 19 2013