A234851 - OEIS

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

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OFFSET

1,2

COMMENTS

Sequence A234695 lists primes in this sequence.

LINKS

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

FORMULA

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

MAPLE

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

PROG

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

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

CROSSREFS

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

Sequence in context: A090422 A005109 A247980 * A179336 A080608 A305352

Adjacent sequences: A234848 A234849 A234850 * A234852 A234853 A234854

KEYWORD

nonn

AUTHOR

M. F. Hasler, Dec 31 2013

STATUS

approved