A103076 - OEIS

%I #15 Jan 17 2019 13:44:07

%S 0,2,20,33,62,68,86,195,524,530,657,1874,2198,62072,73076

%N Numbers n such that 8*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 (74*10^n+43)/9 is prime.

%C a(16) > 10^5. - _Robert Price_, Oct 19 2015

%H Makoto Kamada, <a href="https://stdkmd.net/nrr/8/82227.htm#prime">Prime numbers of the form 822...227</a>.

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

%F a(n) = A101063(n-1) + 1, for n>1.

%t Do[ If[ PrimeQ[(74*10^n + 43)/9], Print[n]], {n, 0, 10000}]

%o (PARI) for(n=0, 1e3, if(isprime((74*10^n+43)/9), print1(n", "))) \\ _Altug Alkan_, Oct 19 2015

%Y Cf. A002275, A101063.

%K more,nonn

%O 1,2

%A _Robert G. Wilson v_, Jan 19 2005

%E Inserted a(1)=0 and added a(14)-a(15) by _Robert Price_, Oct 19 2015