%I #23 Sep 08 2022 08:45:38

%S 3,7,19,31,67,79,127,139,151,199,211,271,307,379,439,547,607,619,691,

%T 727,739,751,787,811,859,907,919,967,991,1039,1087,1231,1279,1447,

%U 1459,1471,1531,1567,1699,1747,1759,1831,1867,1987,2011,2131,2179,2239,2251

%N Primes p such that (p+7)/2 is prime.

%C All these primes are congruent to 3 mod 4 and (with the exception of the first one) to 7 mod 12.

%H Vincenzo Librandi, <a href="/A145472/b145472.txt">Table of n, a(n) for n = 1..1000</a>

%t aa = {}; k = 7; Do[If[PrimeQ[(k + Prime[n])/2], AppendTo[aa, Prime[n]]], {n, 1, 500}];aa

%t Select[Prime[Range[400]],PrimeQ[(#+7)/2]&] (* _Harvey P. Dale_, Jan 11 2020 *)

%o (Magma) [p: p in PrimesUpTo(2500)| IsPrime((p + 7) div 2)]; // _Vincenzo Librandi_, Feb 04 2013

%o (PARI) list(n)=my(t=1, p, i=1); while(i<n, p=prime(i); i=i+1; if(p>2&&isprime((7+p)/2), print1(n, ", "))) \\_Anders Hellström_, Jan 23 2017

%o (PARI) list(lim)=my(v=List()); forprime(p=3,lim, if(isprime((p+7)/2), listput(v,p))); Vec(v) \\ _Charles R Greathouse IV_, Jan 23 2017

%Y Cf. A092109, A145471-A145480, A063910.

%K nonn,easy

%O 1,1

%A _Artur Jasinski_, Oct 11 2008