A128460 Numbers k such that 19^k - 2 is a prime.

1, 2, 3, 13, 14, 19, 20, 23, 38, 1124, 7592, 11755, 12155, 12915, 14172, 15500, 20255, 28388, 184650

Offset: 1

Author

Alexander Adamchuk, Mar 14 2007

Keywords

• nonn
• hard
• more

Comments

No more terms through 50000. - Ryan Propper, Dec 04 2008

a(20) > 2*10^5. - Robert Price, Oct 22 2014

Crossrefs

Cf. A084714 (smallest prime of the form (2n-1)^k - 2).

Cf. A128472 (smallest prime of the form (2n-1)^k - 2 for k > (2n-1)).

Cf. A014224, A109080, A090669, A128455, A128457, A128458, A128459, A128461.

Programs

Magma

[n: n in [0..1000] | IsPrime(19^n-2)]; // Vincenzo Librandi, Oct 23 2014

Mathematica

Do[ f = 19^n - 2; If[ PrimeQ[ f ], Print[ {n, f} ] ], {n,1,1000} ]

Extensions

1124 from Stefan Steinerberger, May 05 2007

7592 from Ryan Propper, Dec 31 2007

Additional terms from Ryan Propper, Dec 04 2008

a(19) from Robert Price, Oct 22 2014