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

1,1

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".

Links

Table of n, a(n) for n=1..19.

Makoto Kamada, List of near-repdigit-related prime numbers.

Index entries for primes involving repunits.

Example

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

Mathematica

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

Prog

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

Crossrefs

Cf. A108330, A108328.

Sequence in context: A029520 A123368 A292164 * A214584 A198131 A200387

Adjacent sequences: A178436 A178437 A178438 * A178440 A178441 A178442

Keyword

more,nonn

Author

Robert Price, Dec 21 2010

Extensions

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

Status

approved