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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, 194471
OFFSET
1,1
COMMENTS
a(27) > 172000. - Robert Price, May 10 2019
Some of the results were computed using the PrimeFormGW (PFGW) primality-testing program. - Hugo Pfoertner, Nov 16 2019
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)/2-2 is prime, A067024 smallest p+2 that has n distinct prime factors, A014545 primorial primes, A087398.
Sequence in context: A037021 A359505 A114741 * A075238 A346408 A158281
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
a(27) from Tyler Busby, Mar 17 2024
STATUS
approved