%I #18 May 05 2016 04:27:02
%S 11,23,53,179,233,317,389,401,443,599,641,683,977,1019,1061,1187,1229,
%T 1409,1481,1523,1619,1787,1997,2069,2111,2657,2963,3299,3329,3371,
%U 3413,3593,3677,3719,4139,4421,4463,5009,5147,5189,5231,5303,5387,5693
%N Primes p such that (p^2 + p + 1)/7 is prime.
%C Primes in A002641.
%H Seiichi Manyama, <a href="/A272628/b272628.txt">Table of n, a(n) for n = 1..1000</a>
%e a(1) = 11 because (11^2+11+1)/7 = 19 is a prime.
%t Select[Prime[Range[5000]], PrimeQ[(#^2 + # + 1) / 7] &]
%o (PARI) lista(nn) = {forprime(p=2, nn, if ((denominator(q=(p^2 + p + 1)/7) == 1) && isprime(q), print1(p, ", ")););} \\ _Michel Marcus_, May 05 2016
%Y Cf. A002641.
%K nonn
%O 1,1
%A _Vincenzo Librandi_, May 04 2016