A102994 - OEIS

%I #17 Jan 17 2019 13:44:07

%S 1,2,7,9,14,24,45,49,73,74,232,338,397,504,1063,2817,5305,16768,27060

%N Numbers n such that 4*10^n + 6*R_n - 5 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

%C Also numbers n such that (14*10^n-17)/3 is prime.

%C a(20) > 10^5. - _Robert Price_, May 27 2015

%H Makoto Kamada, <a href="https://stdkmd.net/nrr/4/46661.htm#prime">Prime numbers of the form 466...661</a>.

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

%F a(n) = A101729(n) + 1.

%t Do[ If[ PrimeQ[(14*10^n - 17)/3], Print[n]], {n, 0, 10000}]

%Y Cf. A002275, A101729.

%K more,nonn

%O 1,2

%A _Robert G. Wilson v_, Jan 17 2005

%E Addition of a(18)-a(19) from Kamada data by _Robert Price_, Dec 10 2010