A119834 Primes p such that 2*p#+1 is prime.

2, 3, 5, 7, 11, 31, 61, 83, 101, 113, 409, 659, 857, 1373, 2711, 5897, 6869, 7699, 32983, 37021, 44491

Offset

1,1

Links

Table of n, a(n) for n=1..21.

Example

2*2 + 1 = 5 (prime), so a(1) = 2;
2*2*3 + 1 = 13 (prime), so a(2) = 3;
2*2*3*5 + 1 = 61 (prime), so a(3) = 5.

Prog

(Magma) [p:p in PrimesUpTo(4000)|IsPrime(2*&*PrimesUpTo(p)+1)]; // Marius A. Burtea, Mar 25 2019

Crossrefs

Cf. A119833, A119835.

Sequence in context: A028867 A104154 A123214 * A095180 A101989 A098922

Adjacent sequences: A119831 A119832 A119833 * A119835 A119836 A119837

Keyword

nonn,more

Author

Pierre CAMI, May 25 2006

Extensions

a(19)-a(21) from Michael S. Branicky, Dec 18 2023

Status

approved