|
%I #18 Jan 17 2019 13:44:07
%S 0,6,9,90,111,210,237,414,1192,1260,5836,6772,24861,52431
%N Numbers n such that 9*10^n + 8*R_n - 7 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
%C Also numbers n such that (89*10^n-71)/9 is prime.
%C a(15) > 10^5. - _Robert Price_, Nov 12 2015
%H Makoto Kamada, <a href="https://stdkmd.net/nrr/9/98881.htm#prime">Prime numbers of the form 988...881</a>.
%H <a href="/index/Pri#Pri_rep">Index entries for primes involving repunits</a>.
%F a(n) = A101016(n-1) + 1, for n > 1.
%t Do[ If[ PrimeQ[(89*10^n - 71)/9], Print[n]], {n, 0, 10000}]
%Y Cf. A002275, A101016.
%K more,nonn
%O 1,2
%A _Robert G. Wilson v_, Jan 19 2005
%E a(13) from Kamada data by _Robert Price_, Dec 14 2010
%E Inserted a(1) = 0 and added a(14) from _Robert Price_, Nov 12 2015
|
