A257790 Numbers k such that 6*5^k - 1 is prime.

0, 1, 2, 5, 11, 28, 65, 72, 361, 479, 494, 599, 1062, 1094, 1193, 2827, 3271, 3388, 3990, 4418, 11178, 16294, 25176, 42500, 68320, 85698, 145259, 159119, 169771, 252665, 412051

Offset

1,3

Comments

All terms correspond to verified primes, that is, not merely probable primes.

Links

Table of n, a(n) for n=1..31.

Mathematica

Select[Range[0, 10000], PrimeQ[6*5^# - 1] &]

Prog

(Magma) [n: n in [0..2*10^3] | IsPrime(6*5^n-1)]; // Vincenzo Librandi, May 09 2015
(PARI) is(n)=ispseudoprime(6*5^n-1) \\ Charles R Greathouse IV, Jun 13 2017

Crossrefs

Cf. A143279.

Sequence in context: A363579 A055227 A325916 * A174145 A358451 A381216

Adjacent sequences: A257787 A257788 A257789 * A257791 A257792 A257793

Keyword

nonn,hard,more

Author

Robert Price, May 08 2015

Extensions

a(30) from Riley Fisher, Sep 20 2024

a(31) from Riley Fisher, Dec 09 2024

Status

approved