A103095 - OEIS

%I #16 Jan 17 2019 13:44:07

%S 1,3,4,15,153,322,471,561,664,2157,3697,14875,19270,22095

%N Numbers n such that 9*10^n + 2*R_n + 5 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

%C Also numbers n such that (83*10^n+43)/9 is prime.

%C a(15) > 10^5. - _Robert Price_, Nov 02 2015

%H Makoto Kamada, <a href="https://stdkmd.net/nrr/9/92227.htm#prime">Prime numbers of the form 922...227</a>.

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

%F a(n) = A101003(n) + 1.

%t Do[ If[ PrimeQ[(83*10^n + 43)/9], Print[n]], {n, 0, 10000}]

%Y Cf. A002275, A101003.

%K more,nonn

%O 1,2

%A _Robert G. Wilson v_, Jan 19 2005

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