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Primes prime(i) such that prime(i) + 2^(i+1) is also prime.
1

%I #19 Jan 02 2019 22:09:48

%S 3,31,71,97,107,277,307,641,907,967,1009,1447,3463,3527,7757,8167,

%T 250867,279047

%N Primes prime(i) such that prime(i) + 2^(i+1) is also prime.

%p for i from 1 do

%p p := ithprime(i) ;

%p if isprime(p+2^(i+1)) then

%p printf("%d,\n",p) ;

%p end if;

%p end do: # _R. J. Mathar_, Jul 12 2014

%t p = 2; lst = {}; While[p < 900000, If[ PrimeQ[ 2^(PrimePi@ p +1) + p], AppendTo[lst, p]; Print@ p]; p = NextPrime@ p]; lst

%o (PARI) lista(nn) = {ip = 1; forprime(p=2, nn, if (isprime(2^(ip+1)+p), print1(p, ", ")); ip++;);} \\ _Michel Marcus_, Jul 12 2014

%Y Cf. A242944, A227126, A228021.

%K nonn,more,hard

%O 1,1

%A _Robert G. Wilson v_, Jul 09 2014