A175172 Primes p such that 3*2^p+1 is also prime.

2, 5, 41, 353

Offset

1,1

Links

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

Formula

A000040 INTERSECT A002253. - R. J. Mathar, Jan 04 2011

Example

For p=2, 3*2^2+1=13; p=5. 3*2^5+1=97; p=41, 3*2^41+1=6597069766657.

Maple

select(p->isprime(p) and isprime(3*2^p+1), [$0..5000]); # Muniru A Asiru, Dec 19 2018

Mathematica

Select[Prime[Range[1000]], PrimeQ[3 2^# + 1] &] (* Vincenzo Librandi, Dec 19 2018 *)

Prog

(Magma) [p: p in PrimesUpTo(4000) | IsPrime(3*2^p+1)]

Crossrefs

Cf. A000040, A002253.

Sequence in context: A185052 A088547 A009457 * A376620 A218057 A126469

Adjacent sequences: A175169 A175170 A175171 * A175173 A175174 A175175

Keyword

nonn,more

Author

Vincenzo Librandi, Mar 09 2010

Status

approved