A234852 - OEIS

%I #5 Jul 14 2024 13:09:56

%S 1,2,3,4,6,7,9,11,13,14,18,20,23,24,27,29,34,36,40,42,46,47,48,53,58,

%T 59,60,62,63,64,66,68,70,71,73,90,95,100,103,105,110,121,122,127,128,

%U 132,133,134,141,143,144,153,155,156,162

%N Indices k of primes p=prime(k) such that prime(p)-p+1 is prime.

%F a(n) = PrimePi(A234695(n)), PrimePi = A000720.

%t Select[Range[200],PrimeQ[Prime[Prime[#]]-Prime[#]+1]&] (* _Harvey P. Dale_, Jul 14 2024 *)

%o (PARI) for(k=1,999,isprime(prime(p=prime(k))-p+1)&&print1(k","))

%Y Cf. A000040, A000720, A014692, A234850, A234851.

%K nonn

%O 1,2

%A _M. F. Hasler_, Dec 31 2013