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%I #22 Sep 08 2022 08:45:03
%S 1,2,3,6,7,11,16,21,24,27,29,30,33,40,43,49,50,51,54,59,60,68,76,78,
%T 90,93,95,103,120,125,131,134,139,156,159,162,168,178,180,188,189,196,
%U 198,214,225,231,237,241,243,246,255,259,268,273,275,277,280,285,287,288
%N Numbers k such that 2*k*prime(k) + 1 is prime.
%H Harry J. Smith, <a href="/A062404/b062404.txt">Table of n, a(n) for n = 1..1000</a>
%e 2*3*prime(3) + 1 = 2 * 3 * 5 + 1 = 31 a prime.
%p select(i->isprime(2*i*ithprime(i)+1),[$1..300]); # _Muniru A Asiru_, Jun 29 2018
%t Select[Range[300],PrimeQ[2# Prime[#]+1]&] (* _Harvey P. Dale_, Sep 12 2014 *)
%o (PARI) select(k->isprime(2*k*prime(k)+1), [1..700])
%o (Magma) [n: n in [1..300] |IsPrime(2*n*NthPrime(n) + 1)]; // _Vincenzo Librandi_, Jun 29 2018
%K nonn
%O 1,2
%A _Jason Earls_, Jul 08 2001
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