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Primes of the form 7 + 2*p, where p is a prime.
1

%I #16 Nov 08 2014 09:42:59

%S 11,13,17,29,41,53,89,101,113,149,173,233,269,281,353,389,401,461,509,

%T 521,569,593,641,701,773,809,929,941,1013,1049,1181,1193,1289,1301,

%U 1361,1373,1409,1493,1553,1601,1721,1733,1889,1901,1913,1949,1973,2069,2129

%N Primes of the form 7 + 2*p, where p is a prime.

%C Starting with n=3 both a(n) and A023206(n) == 5 mod 6. - _Zak Seidov_, Oct 23 2009

%H Vincenzo Librandi, <a href="/A166009/b166009.txt">Table of n, a(n) for n = 1..10000</a>

%F a(n) = 7 + 2*A023206(n). - _R. J. Mathar_, Oct 05 2009

%e 13 is in the sequence because 13 = 7 + 2*3 and 3 are both primes.

%t Clear[lst,n,f] f[n_]:=PrimeQ[(n-1)/2-3]; lst={};Do[p=Prime[n];If[f[p],AppendTo[lst,p]],{n,7!}];lst (* _Vladimir Joseph Stephan Orlovsky_, Oct 13 2009 *)

%t s={11,13};Do[If[PrimeQ[n]&&PrimeQ[(n-7)/2],AppendTo[s,n]],{n,17,10^3,6}];s (* _Zak Seidov_, Oct 23 2009 *)

%t Select[2#+7&/@Prime[Range[200]],PrimeQ] (* _Harvey P. Dale_, Dec 15 2010 *)

%o (PARI) lista(nn) = {forprime(p=2, nn, if (isprime(q=2*p+7), print1(q, ", ")););} \\ _Michel Marcus_, Nov 08 2014

%Y Cf. A023206. - _Zak Seidov_, Oct 23 2009

%K nonn

%O 1,1

%A _Vincenzo Librandi_, Oct 04 2009

%E 1089 replaced with 1049 by _R. J. Mathar_, Oct 05 2009