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Integers k such that 10^k - 39 is prime.
0

%I #32 Jan 25 2022 08:36:38

%S 2,5,6,12,17,19,61,102,195,447,1250,1329,1935,3930,5837,7176,8724,

%T 20881,23936,61868,91920

%N Integers k such that 10^k - 39 is prime.

%C The next term, if one exists, is > 100000. - _Robert Price_, Apr 25 2011

%C See Kamada link - primecount.txt for terms, primesize.txt for discovery details including probable or proved primes - search on "99961".

%H Makoto Kamada, <a href="https://stdkmd.net/nrr/prime/">List of near-repdigit-related prime numbers</a>.

%H <a href="/index/Pri#Pri_rep">Index entries for primes involving repunits</a>.

%e k=2 is a term because 10^2 - 39 = 61 (prime).

%e k=61 is a term because 10^61 - 39 = 9999999999999999999999999999999999999999999999999999999999961 (prime).

%Y Cf. A108330, A108328.

%K nonn,more

%O 1,1

%A _Parthasarathy Nambi_, Jul 01 2005

%E a(8)-a(12) from _Stefan Steinerberger_, Nov 05 2005

%E a(13)-a(19) from _Robert Price_, Dec 12 2010

%E Edited by _Ray Chandler_, Dec 23 2010

%E a(20)-a(21) from _Robert Price_, Apr 25 2011