A267943 - OEIS

%I #13 Sep 08 2022 08:46:15

%S 3,4,6,94

%N Numbers n such that 2^n - 3 and 3*2^n - 1 are both prime.

%C The intersection of A002235 and A050414 is not empty (3 does not belong to A267985).

%F A002235 INTERSECT A050414.

%e a(3) = 6 because 2^6 - 3 = 61 and 3*2^6 - 1 = 191 are both prime.

%o (Magma) [n: n in [2..94] | IsPrime(2^n-3) and IsPrime(3*2^n-1)];

%o (PARI) isok(n) = isprime(2^n-3) && isprime(3*2^n-1);

%Y Cf. A002235, A007505, A050414, A050415, A238694, A267985.

%K nonn,hard,more

%O 1,1

%A _Arkadiusz Wesolowski_, Jan 22 2016