A093713 Numbers k such that 6^k - 5^(k-1) is prime.

1, 2, 3, 4, 5, 12, 16, 18, 21, 42, 66, 69, 123, 132, 165, 204, 397, 401, 486, 657, 1005, 1050, 1882, 2545, 2813, 3168, 4092, 4151, 4469, 5358, 9168, 11554, 11866, 80946

Offset: 1

Author

Herman H. Rosenfeld (herm3(AT)pacbell.net) and Robert G. Wilson v, Jun 17 2004

Keywords

• nonn
• more

Comments

a(35) > 10^5. - Robert Price, May 04 2016

Crossrefs

Cf. A093765.

Programs

Mathematica

Do[ If[ PrimeQ[6^n - 5^(n - 1)], Print[n]], {n, 2000}]

PARI

is(n)=isprime(6^n-5^(n-1)) \\ Charles R Greathouse IV, Feb 17 2017

Extensions

a(24)-a(34) from Robert Price, May 04 2016