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%I #23 Jan 17 2019 13:44:08
%S 2,3,4,5,7,9,10,14,22,98,127,151,158,274,377,1015,2146,8499,13885,
%T 13991,17834,18211,36271,52317,53804,104212,117059,178695
%N Numbers n such that 10^n - 71 is prime.
%C a(29) > 2.5*10^5. - _Robert Price_, Apr 12 2015
%H Makoto Kamada, <a href="https://stdkmd.net/nrr/aaaba.htm">Near-repdigit numbers of the form AA...AABA</a>.
%H Makoto Kamada, <a href="https://stdkmd.net/nrr/9/99929.htm#prime">Prime numbers of the form 99...9929</a>.
%H <a href="/index/Pri#Pri_rep">Index entries for primes involving repunits</a>.
%e 10^4 - 71 = 9929 which is a prime number.
%t nMax=1000; Do[If[PrimeQ[10^n-71], Print[n]], {n, nMax}]
%o (PARI) is(n)=ispseudoprime(10^n-71) \\ _Charles R Greathouse IV_, Jun 13 2017
%Y Cf. A108330, A108328.
%K more,nonn
%O 1,1
%A _Robert Price_, Dec 21 2010
%E a(24:25)=52317,53804 from _Robert Price_, Apr 25 2011
%E a(26)-a(28) from Kamada data by _Robert Price_, Apr 12 2015
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