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%I #18 Sep 08 2022 08:45:12
%S 7,13,17,29,37,41,61,89,97,109,137,149,181,197,229,257,277,281,317,
%T 337,349,389,397,401,449,457,461,541,557,569,617,677,701,709,761,769,
%U 797,821,881,929,937,977,1009,1021,1049,1097,1117,1129,1201,1217,1229,1237
%N Primes p such that (p-3)/2 is also prime.
%H Vincenzo Librandi, <a href="/A089531/b089531.txt">Table of n, a(n) for n = 1..1000</a>
%F a(n) = 2*A023204(n) + 3.
%t Clear[lst,n,f] f[n_]:=PrimeQ[(n-3)/2]; lst={};Do[p=Prime[n];If[f[p],AppendTo[lst,p]],{n,6!}];lst (* _Vladimir Joseph Stephan Orlovsky_, Oct 13 2009 *)
%t Select[Prime[Range[300]], PrimeQ[(# - 3) / 2]&] (* _Vincenzo Librandi_, Apr 13 2013 *)
%o (Magma) [p: p in PrimesUpTo(1300) | IsPrime((p-3) div 2)]; // _Vincenzo Librandi_, Apr 13 2013
%o (PARI) is(n)=isprime(n) && isprime((n-3)\2) \\ _Charles R Greathouse IV_, Sep 09 2014
%Y Cf. A023204, A089530, A089532.
%K nonn,easy
%O 1,1
%A _Ray Chandler_, Nov 07 2003
%E Comment from _Juri-Stepan Gerasimov_ used as new name (old name moved to formulas). - _Charles R Greathouse IV_, Sep 09 2014
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