A093765 Numbers k such that 6^k+5^(k-1) is prime.

1, 2, 3, 8, 9, 15, 26, 30, 69, 212, 318, 909, 1224, 1946, 2192, 2234, 2978, 3344, 4976, 7947, 8079, 23334, 23624, 55401, 89712

Offset: 1

Author

Herman H. Rosenfeld (herm3(AT)pacbell.net), May 17 2004

Keywords

• nonn
• hard
• more

Comments

a(26) > 10^5. - Robert Price, Feb 13 2016

Examples

			15 is a member since 615+515 = 476288500201 which is a prime number.
		

Crossrefs

Cf. A093713, A082103, A093717, A093793, A096185, A093794, A093795, A096186.

Programs

Mathematica

Do[ If[ PrimeQ[6^n + 5^(n - 1)], Print[n]], {n, 4000}]

PARI

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

Extensions

More terms from Robert G. Wilson v, Jun 18 2004

a(19)-a(25) from Robert Price, Feb 13 2016