A096594 Numbers n such that 100^n + 10^n - 1 is prime.

1, 2, 3, 5, 6, 7, 9, 13, 26, 42, 153, 188, 204, 282, 699, 2886, 11597

Offset: 1

Author

Jason Earls, Aug 13 2004

Keywords

• more
• nonn

Comments

a(1) through a(17) have been proved to be prime with WinPFGW or pfgw.

a(18) > 20000. - Giovanni Resta, Feb 19 2013

a(18) > 100000. - James G. Merickel Jun 02 2014

Examples

			a(3) = 3 because 100^3 + 10^3 - 1 = 1000999, a prime.
		

Programs

Mathematica

Select[Range[700], PrimeQ[100^# + 10^# - 1] & ] (* Giovanni Resta, Feb 19 2013 *)

PARI

is(n)=ispseudoprime(100^n+10^n-1) \\ Charles R Greathouse IV, Feb 20 2017

Extensions

a(17) from Giovanni Resta, Feb 19 2013