A267943 Numbers n such that 2^n - 3 and 3*2^n - 1 are both prime.

3, 4, 6, 94

Offset

1,1

Comments

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

Links

Table of n, a(n) for n=1..4.

Formula

A002235 INTERSECT A050414.

Example

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

Prog

(Magma) [n: n in [2..94] | IsPrime(2^n-3) and IsPrime(3*2^n-1)];
(PARI) isok(n) = isprime(2^n-3) && isprime(3*2^n-1);

Crossrefs

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

Sequence in context: A358936 A256326 A239244 * A066466 A332511 A129293

Adjacent sequences: A267940 A267941 A267942 * A267944 A267945 A267946

Keyword

nonn,hard,more

Author

Arkadiusz Wesolowski, Jan 22 2016

Status

approved