A234851 Indices of primes in A014692, i.e., numbers k such that prime(k)-k+1 is prime.

1, 2, 3, 5, 7, 13, 17, 21, 23, 25, 31, 41, 43, 49, 61, 71, 77, 83, 89, 103, 105, 109, 121, 129, 133, 139, 151, 161, 173, 181, 183, 185, 189, 199, 211, 213, 223, 231, 235, 241, 243, 247, 265, 271, 273, 277, 279, 281, 285, 293, 301, 303, 307, 311, 317

Offset: 1

Author

M. F. Hasler, Dec 31 2013

Keywords

• nonn

Comments

Sequence A234695 lists primes in this sequence.

Links

• Robert Israel, Table of n, a(n) for n = 1..10000

Crossrefs

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

Programs

Maple

select(k -> isprime(ithprime(k)-k+1), [$1..1000]); # Robert Israel, Feb 19 2021

PARI

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

PARI

is_A234851(n)=isprime(prime(k)-k+1)

Formula

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