OFFSET

1,2

COMMENTS

According to Maple version 14, the next entries are 534, 620 and 803, but these involve primes of 256 and more digits and may not be certified primes. - R. J. Mathar, Sep 23 2011

a(19) > 10^5, if it exists. - Michael S. Branicky, Aug 26 2024

EXAMPLE

1 is in the sequence because 2*3^1-2*1-1 = 3 is a prime.

2 is in the sequence because 2*3^2-2*2-1 = 13 is a prime.

3 is in the sequence because 2*3^3-2*3-1=47 ts a prime.

4 is not in the sequence because 2*3^4-2*4-1 = 153 = 3^2*17 is not prime.

PROG

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

CROSSREFS

KEYWORD

nonn,more

AUTHOR

Juri-Stepan Gerasimov, Sep 23 2011

EXTENSIONS

a(10)-a(18) from Michael S. Branicky, Jul 14 2023

STATUS

approved