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A178439 Numbers n such that 10^n - 99 is prime. 0
4, 5, 7, 27, 91, 248, 347, 501, 535, 767, 2002, 2581, 2677, 8158, 15977, 20666, 23854, 72730, 86816 (list; graph; refs; listen; history; text; internal format)
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

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Last modified September 26 05:09 EDT 2017. Contains 292502 sequences.