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%I #15 Sep 08 2022 08:46:07
%S 1,2,11,24,28,92,166,191,220,587,677,964,988,1840,2664,3604,6079,6640,
%T 8817,33647,34308,39882,44055,47050,64100,103313,223439,225921
%N Numbers k such that prime(k) * 2^k - 1 is prime.
%C The PFGW program has been used to certify all the terms up to a(28), using a deterministic test which exploits the factorization of a(n)+1.
%C a(29) > 290000.
%t Select[Range[1000], PrimeQ[Prime[#]*2^# - 1] &]
%o (Magma) [n: n in [0..1000] | IsPrime(NthPrime(n)*2^n-1)]; // _Vincenzo Librandi_, Dec 24 2015
%o (PARI) is(n,p=prime(n))=ispseudoprime(p<<n-1) \\ _Charles R Greathouse IV_, Jun 06 2017
%Y Cf. A239742.
%K nonn,more
%O 1,2
%A _Giovanni Resta_, Mar 26 2014
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