A102944 - OEIS

%I #24 Jul 08 2021 03:09:44

%S 1,16,22,28,34,90,2068,2374,2854,3720,4242,22666,29292,29508

%N Numbers k such that 10^k + 8*R_k - 5 is prime, where R_k = 11...1 is the repunit (A002275) of length k.

%C Also numbers k such that (17*10^k - 53)/9 is prime.

%C a(15) > 10^5. - _Robert Price_, Feb 11 2015

%H Makoto Kamada, <a href="https://stdkmd.net/nrr/1/18883.htm#prime">Prime numbers of the form 188...883</a>.

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

%F a(n) = A102030(n) + 1.

%t Do[ If[ PrimeQ[(17*10^n - 53)/9], Print[n]], {n, 0, 10000}]

%Y Cf. A002275, A102030.

%K more,nonn

%O 1,2

%A _Robert G. Wilson v_, Dec 16 2004

%E Addition of a(12)-a(14) from Kamada data by _Robert Price_, Dec 12 2010