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%I #24 Mar 20 2024 11:11:27
%S 2,3,5,7,13,29,31,37,47,59,109,223,307,389,457,1117,1151,2273,9137,
%T 10753,15727,25219,26459,29251,30259,52901,194471
%N Primes p such that primorial(p)/2 + 2 is prime.
%C a(27) > 172000. - _Robert Price_, May 10 2019
%C Some of the results were computed using the PrimeFormGW (PFGW) primality-testing program. - _Hugo Pfoertner_, Nov 16 2019
%e a(3)=7 because primorial(7)/2 + 2 = A070826(4) + 2 = 2*3*5*7/2 + 2 = 107 is prime.
%t k = 1; Do[If[PrimeQ[n], k = k*n; If[PrimeQ[k/2 + 2], Print[n]]], {n, 2, 100000}] (* _Ryan Propper_, Jul 03 2005 *)
%o (PARI) P=1/2;forprime(p=2,1e4,if(isprime((P*=p)+2), print1(p", "))) \\ _Charles R Greathouse IV_, Mar 14 2011
%Y 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.
%K more,nonn
%O 1,1
%A _Hugo Pfoertner_, Jun 27 2004
%E 7 additional terms, corresponding to probable primes, from _Ryan Propper_, Jul 03 2005
%E Edited by _T. D. Noe_, Oct 30 2008
%E a(26) from _Robert Price_, May 10 2019
%E a(27) from _Tyler Busby_, Mar 17 2024
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