A057665 - OEIS

%I #31 Sep 01 2024 10:28:43

%S 2,3,24,66,126

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

%C a(6) > 3002, since prime(3002) = 27479 (see comment by _Ralf Stephan_ in A057663). - _Michel Marcus_, Dec 20 2013

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

%C If it exists, a(6) > 15*10^3. - _Michal Paulovic_, Sep 24 2023

%C If it exists, a(6) > 30*10^3. - _Michael S. Branicky_, Sep 01 2024

%F a(n) = primepi(A057663(n)). - _Michel Marcus_, Dec 20 2013

%t Select[Range[10^3], PrimeQ[# + 2^#] &@ Prime@ # &] (* _Michael De Vlieger_, Oct 26 2017 *)

%o (PARI) isok(n) = isprime(prime(n) + 2^prime(n)); \\ _Michel Marcus_, Dec 19 2013

%Y Cf. A052007, A057663, A057664.

%K nonn,more,hard

%O 1,1

%A _Labos Elemer_, Oct 16 2000

%E Name edited by _Michel Marcus_, Dec 19 2013