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%I #23 Jan 17 2019 13:44:06
%S 1,2,14,20,30,44,66,260,872,8846,26744,57506,98472,106892
%N Numbers n such that 4*10^n-3 is prime.
%C See Kamada link for search limit and prime vs. PRP status.
%C a(14) > 10^5. - _Robert Price_, Mar 17 2015.
%C a(15) > 2*10^5. - _Robert Price_, Oct 02 2015
%H Makoto Kamada, <a href="https://stdkmd.net/nrr/3/39997.htm#prime">Prime numbers of the form 399...997</a>.
%H <a href="/index/Pri#Pri_rep">Index entries for primes involving repunits</a>.
%F a(n) = A101849(n) + 1.
%e n = 1, 2, 14, 20 are members since 37, 397, 399999999999997 and 399999999999999999997
%e are prime numbers.
%t Do[ If[ PrimeQ[4*10^n - 3], Print[n]], {n, 0, 10000}]
%o (PARI) for(n=1, 1e4, if(isprime(4*10^n-3), print1(n", "))) \\ _Altug Alkan_, Oct 02 2015
%Y Cf. A089675, A101849.
%K nonn
%O 1,2
%A Julien Peter Benney (jpbenney(AT)ftml.net), Jan 15 2005
%E a(11)-a(12) from Kamada data by _Robert Price_, Dec 13 2010
%E a(13) from Kamada data by _Robert Price_, Mar 17 2015
%E a(14) from _Robert Price_, Oct 02 2015
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