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%I #9 Jan 31 2020 12:26:52
%S 5,11,107,179,347,479,1187,1307,1367,1487,1619,2027,2207,2447,2999,
%T 3119,3467,4007,4079,4139,4799,5087,5807,5927,5939,6827,7079,7247,
%U 8699,9587,9839,10607,12107,12539,12659,14207,15299,16139,16187,17027
%N Safe primes (A005385) (p and (p-1)/2 are primes) such that 8*p+1 (A023228) is also prime.
%H Harvey P. Dale, <a href="/A075706/b075706.txt">Table of n, a(n) for n = 1..1000</a>
%e 11 is a prime, so is (11-1)/2=5 and also 8*11+1=89; 107 is a prime, (107-1)/2=53 and 8*107+1=857, ...
%p ts_sg8_var_pras := proc(nmax) local i,tren,atek; tren := 0: for i from 1 to nmax do atek := numtheory[safeprime](i): if (atek > tren) then if (isprime(atek)='true' and isprime(6*atek+1)='true') then tren := atek: fi; fi; od; end: seq(ts_sg8_var_pras(i), i=1..3000);
%t Select[Prime[Range[2000]],AllTrue[{(#-1)/2,8#+1},PrimeQ]&] (* The program uses the AllTrue function from Mathematica version 10 *) (* _Harvey P. Dale_, Jan 31 2020 *)
%o (PARI) forprime(p=3,20000,if(isprime((p-1)/2),if(isprime(8*p+1),print1(p","))))
%Y Cf. A005384, A005385, A059455, A023228.
%K nonn
%O 1,1
%A _Jani Melik_, Oct 02 2002
%E More terms from _Ralf Stephan_, Mar 19 2003