|
%I #16 Jan 17 2019 13:44:07
%S 3,5,15,47,69,123,713,2316,6147,8877,10704
%N Numbers n such that 6*10^n + 7*R_n + 2 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
%C Also numbers n such that (61*10^n+11)/9 is prime.
%C a(12) > 10^5. - _Robert Price_, Sep 15 2015
%H Makoto Kamada, <a href="https://stdkmd.net/nrr/6/67779.htm#prime">Prime numbers of the form 677...779</a>.
%H <a href="/index/Pri#Pri_rep">Index entries for primes involving repunits</a>.
%F a(n) = A101536(n) + 1.
%t Do[ If[ PrimeQ[(61*10^n + 11)/9], Print[n]], {n, 0, 10000}]
%Y Cf. A002275, A101536.
%K more,nonn
%O 1,1
%A _Robert G. Wilson v_, Jan 18 2005
%E a(11) from Kamada data by _Robert Price_, Dec 14 2010
|
