A092767 Numbers k such that 10^k - 11 is prime.

2, 5, 8, 12, 15, 18, 20, 30, 80, 143, 152, 164, 176, 239, 291, 324, 504, 594, 983, 2894, 22226, 35371, 58437, 67863, 180979

Offset: 1

Author

Carl R. White, Apr 23 2004

Keywords

• more
• nonn

Comments

Some of the larger terms may only correspond to probable primes.

The numbers corresponding to k = 324, 504, 594 & 983 are certified prime by Primo. - Robert G. Wilson v, Jul 01 2005

a(26) > 2.5*10^5. - Robert Price, Apr 12 2015

Examples

			k = 5 is a term because 10^5 - 11 = 100000 - 11 = 99989, which is prime.
		

Links

• Makoto Kamada, Near-repdigit numbers of the form AA...AABA.
• Makoto Kamada, Prime numbers of the form 99...9989.
• Index entries for primes involving repunits.

Crossrefs

Cf. A089675, A086865, A004023, A095714.

Programs

Mathematica

Do[ If[ PrimeQ[10^n - 11], Print[n]], {n, 3000}] (* Robert G. Wilson v, Jul 01 2005 *)

PARI

for(n=0,5000,if(isprime(10^n-11),print1(n,","))) \\ Ryan Propper, Jun 15 2005

Extensions

4 more terms from Ryan Propper, Jun 15 2005

Edited by N. J. A. Sloane, May 04 2007

a(21)-a(22) from Robert Price, Dec 12 2010

Edited by Ray Chandler, Dec 23 2010

a(23)=58437 and a(24)=67863 from Robert Price, May 29 2011

a(25) from Kamada data by Robert Price, Apr 12 2015