

A096177


Primes p such that primorial(p)/2 + 2 is prime.


7



2, 3, 5, 7, 13, 29, 31, 37, 47, 59, 109, 223, 307, 389, 457, 1117, 1151, 2273, 9137, 10753, 15727, 25219, 26459, 29251, 30259, 52901
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OFFSET

1,1


COMMENTS

a(27) > 172000.  Robert Price, May 10 2019
Some of the results were computed using the PrimeFormGW (PFGW) primalitytesting program.  Hugo Pfoertner, Nov 16 2019


LINKS

Table of n, a(n) for n=1..26.


EXAMPLE

a(3)=7 because primorial(7)/2 + 2 = A070826(4) + 2 = 2*3*5*7/2 + 2 = 107 is prime.


MATHEMATICA

k = 1; Do[If[PrimeQ[n], k = k*n; If[PrimeQ[k/2 + 2], Print[n]]], {n, 2, 100000}] (* Ryan Propper, Jul 03 2005 *)


PROG

(PARI) P=1/2; forprime(p=2, 1e4, if(isprime((P*=p)+2), print1(p", "))) \\ Charles R Greathouse IV, Mar 14 2011


CROSSREFS

Cf. A070826, A096178 primes of the form primorial(p)/2+2, A096547 primes p such that primorial(p)/22 is prime, A067024 smallest p+2 that has n distinct prime factors, A014545 primorial primes, A087398.
Sequence in context: A135372 A037021 A114741 * A075238 A158281 A115261
Adjacent sequences: A096174 A096175 A096176 * A096178 A096179 A096180


KEYWORD

more,nonn


AUTHOR

Hugo Pfoertner, Jun 27 2004


EXTENSIONS

7 additional terms, corresponding to probable primes, from Ryan Propper, Jul 03 2005
Edited by T. D. Noe, Oct 30 2008
a(26) from Robert Price, May 10 2019


STATUS

approved



