A058037 Numbers k such that 3^k - k is prime.

1, 2, 8, 20, 40, 104, 110, 208, 472, 832, 1982, 25628, 235532

Offset: 1

Author

Robert G. Wilson v, Nov 16 2000

Keywords

• nonn
• more

Comments

Except for the first term all terms are of the form 6m+2 or 6m+4. There are no further terms up to 34500. - Farideh Firoozbakht, Jul 17 2005

a(13) > 2*10^5. - Robert Price, Feb 05 2014

Programs

Mathematica

Do[ If[ PrimeQ[ 3^n - n ], Print[ n ] ], {n, 0, 3000} ]

PARI

for(k=1, 10^6, if(ispseudoprime(3^k-k), print1(k, ", "))); /* Joerg Arndt, Apr 07 2013 */

Extensions

a(12) from Farideh Firoozbakht, Jul 17 2005

a(13) from Nico Puada, Sep 18 2023