A108328 Integers k such that 10^k - 23 is a prime number.

3, 11, 17, 23, 35, 161, 765, 3473, 6887, 27681, 34313

Offset

1,1

Comments

See Kamada link - primecount.txt for terms, primesize.txt for discovery details including probable or proved primes - search on "99977".

No other terms < 100000. - Robert Price, Mar 03 2011

Links

Table of n, a(n) for n=1..11.

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

Index entries for primes involving repunits.

Example

n = 3 is a member because 10^3 - 23 = 1000 - 23 = 977, which is prime.

Mathematica

lst={}; Do[If[PrimeQ[10^n-23], AppendTo[lst, n]], {n, 0, 10^4}]; lst (* Vladimir Joseph Stephan Orlovsky, Aug 19 2008 *)

Crossrefs

Cf. A089675, A095714, A092767.

Sequence in context: A165561 A038960 A019397 * A153419 A079020 A118590

Adjacent sequences: A108325 A108326 A108327 * A108329 A108330 A108331

Keyword

nonn,hard,more

Author

Julien Peter Benney (jpbenney(AT)ftml.net), Jun 30 2005

Extensions

a(9)-a(11) from Robert Price, Dec 13 2010

Edited by Ray Chandler, Dec 23 2010

Status

approved