A178439 Numbers n such that 10^n - 99 is prime.

4, 5, 7, 27, 91, 248, 347, 501, 535, 767, 2002, 2581, 2677, 8158, 15977, 20666, 23854, 72730, 86816

Offset: 1

Author

Robert Price, Dec 21 2010

Keywords

• more
• nonn

Comments

The next term, if it exists, is > 100000.

See Kamada link - primecount.txt for terms, primesize.txt for discovery details including probable or proved primes - search on "99901".

Examples

			10^4 - 99 = 9901 which is a prime number.
		

Links

• Makoto Kamada, List of near-repdigit-related prime numbers.
• Index entries for primes involving repunits.

Crossrefs

Cf. A108330, A108328.

Programs

Mathematica

nMax=1000; Do[If[PrimeQ[10^n-99], Print[n]], {n, nMax}]

PARI

is(n)=ispseudoprime(10^n-99) \\ Charles R Greathouse IV, Jun 13 2017

Extensions

a(18-19)=72730,86816 from Robert Price, May 29 2011