A195815 Numbers k such that 2*(3^k-2*k)+1 is prime.

1, 2, 3, 5, 11, 188, 509, 1730, 2571, 3402, 4407, 9890, 18609, 20456, 32529, 38124, 95087

Offset

1,2

Comments

The associated primes are 3, 11, 43, 467, 354251,....

Links

Table of n, a(n) for n=1..17.

Example

a(1)=1 because 2*(3^1-2*1)+1=3 is a prime, a(2)=2 because 2*(3^2-2*2)+1=11 is a prime, a(3)=3 because 2*(3^3-2*3)+1=43 is a prime, a(4)=5 because 2*(3^5-2*5)+1=467 is a prime, a(5)=11 because 2*(3^11-2*11)+1=354251 is a prime.

Prog

(PARI) is(n)=ispseudoprime(2*(3^n-2*n)+1) \\ Charles R Greathouse IV, Jun 13 2017

Crossrefs

Cf. A195732.

Sequence in context: A118573 A051835 A075883 * A327428 A220346 A391121

Adjacent sequences: A195812 A195813 A195814 * A195816 A195817 A195818

Keyword

nonn,more

Author

Juri-Stepan Gerasimov, Sep 24 2011

Extensions

a(9)-a(16) from Michael S. Branicky, Jul 15 2023

a(17) from Michael S. Branicky, Aug 25 2024

Status

approved