A157977 - OEIS

%I #17 Sep 08 2022 08:45:42

%S 2,3,11,17,23,29,41,71,101,149,167,233,239,251,263,269,281,293,317,

%T 347,353,401,449,461,491,503,557,563,569,647,683,743,797,857,941,947,

%U 953,977,1019,1031,1091,1103,1151,1163,1193,1217,1283,1289,1319,1361,1373

%N Primes p such that 20*p + 19 is also prime.

%H Vincenzo Librandi, <a href="/A157977/b157977.txt">Table of n, a(n) for n = 1..2000</a>

%t q=19;lst={};Do[p=Prime[n];If[PrimeQ[(q+1)*p+q],AppendTo[lst,p]],{n,6!}];lst

%t Select[Prime[Range[250]],PrimeQ[20#+19]&] (* _Harvey P. Dale_, Jul 04 2011 *)

%o (Magma) [n: n in [0..2000] | IsPrime(n) and IsPrime(20*n + 19)]; // _Vincenzo Librandi_, Feb 03 2014

%Y Cf. A136082, A136083, A023213, A023221, A023235, A023240, A157974, A136083, A136084, A136085, A136086, A136087, A089440, A157975, A157976.

%K nonn,easy

%O 1,1

%A _Vladimir Joseph Stephan Orlovsky_, Mar 10 2009