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A267943 Numbers n such that 2^n - 3 and 3*2^n - 1 are both prime. 0
3, 4, 6, 94 (list; graph; refs; listen; history; text; internal format)
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: A263940 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

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Last modified July 12 04:30 EDT 2020. Contains 335658 sequences. (Running on oeis4.)