A234851 - OEIS

%I #11 Feb 19 2021 14:36:34

%S 1,2,3,5,7,13,17,21,23,25,31,41,43,49,61,71,77,83,89,103,105,109,121,

%T 129,133,139,151,161,173,181,183,185,189,199,211,213,223,231,235,241,

%U 243,247,265,271,273,277,279,281,285,293,301,303,307,311,317

%N Indices of primes in A014692, i.e., numbers k such that prime(k)-k+1 is prime.

%C Sequence A234695 lists primes in this sequence.

%H Robert Israel, <a href="/A234851/b234851.txt">Table of n, a(n) for n = 1..10000</a>

%F a(n) = PrimePi(A234850(n)), PrimePi = A000720.

%p select(k -> isprime(ithprime(k)-k+1), [$1..1000]); # _Robert Israel_, Feb 19 2021

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

%o (PARI) is_A234851(n)=isprime(prime(k)-k+1)

%Y Cf. A000040, A000720, A014692, A234695, A234850, A234852.

%K nonn

%O 1,2

%A _M. F. Hasler_, Dec 31 2013