Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).
%I #11 Mar 24 2014 23:55:01
%S 5,23,59,83,383,479,503,719,839,863,1619,2039,2099,2579,2819,2879,
%T 3023,4139,4259,4679,4703,4919,5879,6719,6779,7559,8039,8783,8819,
%U 10799,11279,11423,12203,12659,12899,12983,13523,13799,14159,14303,14699,15683,18119,18443,19259,19379,20183,20663,21059,23663,24083,24239,24659,27239,28163,29123,29339,29483,29759,30803,31139,31583,36923,37463,38603,39119,39503,39839,39983,41879,42299,42443,43403,44519,44939,46679,47339,47819,47963
%N Safe primes (A005385) (p and (p-1)/2 are primes) such that 12*p+1 is also prime.
%e 23 is a prime, so is (23-1)/2=11 and also 12*23+1=277, 59 is a prime, (59-1)/2=29 and 12*59+1=709, ...
%p ts_sgB_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_sgB_var_pras(i), i=1..3000);
%t okQ[n_]:=PrimeQ[(n-1)/2]&&PrimeQ[12n+1]
%t Select[Prime[Range[5000]],okQ] (* _Harvey P. Dale_, Nov 21 2010 *)
%Y Cf. A005384, A005385, A059455.
%K nonn
%O 1,1
%A _Jani Melik_, Oct 02 2002
%E More terms from _Harvey P. Dale_, Nov 21 2010