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Primes p such that 2*p#+1 is prime.
2

%I #18 Dec 19 2023 01:35:14

%S 2,3,5,7,11,31,61,83,101,113,409,659,857,1373,2711,5897,6869,7699,

%T 32983,37021,44491

%N Primes p such that 2*p#+1 is prime.

%e 2*2 + 1 = 5 (prime), so a(1) = 2;

%e 2*2*3 + 1 = 13 (prime), so a(2) = 3;

%e 2*2*3*5 + 1 = 61 (prime), so a(3) = 5.

%o (Magma) [p:p in PrimesUpTo(4000)|IsPrime(2*&*PrimesUpTo(p)+1)]; // _Marius A. Burtea_, Mar 25 2019

%Y Cf. A119833, A119835.

%K nonn,more

%O 1,1

%A _Pierre CAMI_, May 25 2006

%E a(19)-a(21) from _Michael S. Branicky_, Dec 18 2023