A192611 Primes prime(k) such that prime(k)*k+1 is also prime.

2, 3, 7, 13, 89, 113, 151, 181, 359, 433, 521, 541, 641, 701, 719, 827, 953, 1033, 1277, 1301, 1439, 1877, 2069, 2111, 2143, 2267, 2357, 2423, 2791, 2801, 2861, 2887, 3191, 3251, 3313, 3557, 3643, 3739, 3797, 3821, 3863, 3931, 3947, 4021, 4447

Offset

1,1

Comments

Primes p such that p*pi(p)+1 is prime (see Crossrefs).

Links

Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

Example

13 is in the list because, being the 6th prime, 13*6+1=79 is prime.

Mathematica

Select[Prime[Range[700]], PrimeQ[# PrimePi[#]+1]&] (* Harvey P. Dale, May 28 2012 *)

Prog

(Magma) [ NthPrime(n): n in [1..650] | IsPrime(NthPrime(n)*n+1) ]; // Bruno Berselli, Jul 05 2011
(PARI) k=0; forprime(p=2, 1e4, if(isprime(k++*p+1), print1(p", "))) \\ Charles R Greathouse IV, Jul 05 2011

Crossrefs

Cf. A096064, A086172.

Cf. A000040 The prime numbers.

Cf. A000720 pi(n), the number of primes <= n.

Sequence in context: A049536 A065508 A078154 * A254461 A048463 A006695

Adjacent sequences: A192608 A192609 A192610 * A192612 A192613 A192614

Keyword

nonn

Author

Andrea Raffetti, Jul 05 2011

Status

approved