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A092058 Numbers n such that 2*prime(n)^2 - 1 is prime.

%I A092058 #14 Sep 08 2022 08:45:13
%S A092058 1,2,4,5,6,7,13,14,17,21,29,30,31,33,37,41,42,45,46,47,54,56,59,62,64,
%T A092058 71,73,75,80,81,84,93,103,105,106,113,114,120,126,131,132,134,139,141,
%U A092058 144,145,146,148,159,160,169,175,179,183,185,186,188,192,212,217,220
%N A092058 Numbers n such that 2*prime(n)^2 - 1 is prime.
%H A092058 Vincenzo Librandi, <a href="/A092058/b092058.txt">Table of n, a(n) for n = 1..1000</a>
%F A092058 A106483(n) = prime(a(n)) . - _R. J. Mathar_, Aug 20 2019
%e A092058 2*prime(1)^2 - 1 = 7 is prime so a(1)=1;
%e A092058 2*prime(2)^2 - 1 = 17 is prime so a(2)=2;
%e A092058 2*prime(3)^2 - 1 = 97 is not prime;
%e A092058 2*prime(4)^2 - 1 = 241 is prime so a(3)=4.
%t A092058 Select[Range[500],PrimeQ[2Prime[#]^2-1]&] (* _Harvey P. Dale_, Dec 13 2010 *)
%o A092058 (PARI) for (i=1,300,if(isprime(2*prime(i)^2-1),print1(i,",")))
%o A092058 (Magma) [n: n in [1..220]| IsPrime(2*NthPrime(n)^2-1)]; // _Vincenzo Librandi_, Jan 18 2013
%Y A092058 Cf. A092057.
%K A092058 easy,nonn
%O A092058 1,2
%A A092058 mohammed Bouayoun (mohammed.bouayoun(AT)sanef.com), Feb 19 2004