A108320 Numbers k such that 609 * 10^k - 1 is prime.

1, 2, 3, 4, 5, 6, 12, 17, 43, 46, 50, 88, 110, 187, 472, 832, 834, 1034, 1311, 1700, 2756, 5470, 6124, 7404, 7891, 12010, 16411, 24576, 25461, 27982, 38762

Offset: 1

Author

Jason Earls, Jun 30 2005

Keywords

• more
• nonn

Examples

			a(4) = 4 because 609*10^4-1 = 6089999, a prime.
		

Crossrefs

Cf. A053580.

Programs

PARI

is(n)=ispseudoprime(609*10^n-1) \\ Charles R Greathouse IV, Jun 13 2017

Extensions

a(27) from Michael S. Branicky, May 19 2023

a(28)-a(31) from Michael S. Branicky, Oct 29 2024