%I A102983
%S A102983 2,5,77,206,1871,3887
%N A102983 Numbers n such that 4*10^n + R_n + 8 is prime, where R_n = 11...1 is 
               the repunit (A002275) of length n.
%C A102983 Also numbers n such that (37*10^n+71)/9 is prime.
%H A102983 Makoto Kamada, <a href="http://homepage2.nifty.com/m_kamada/math/41119.htm">
               Factorizations of 411...119</a>.
%H A102983 <a href="Sindx_Pri.html#Pri_rep">Index entries for primes involving repunits</
               a>.
%t A102983 Do[ If[ PrimeQ[(37*10^n + 71)/9], Print[n]], {n, 0, 10000}]
%Y A102983 Sequence in context: A007506 A042693 A128297 this_sequence A038583 A082080 
               A127997
%Y A102983 Adjacent sequences: A102980 A102981 A102982 this_sequence A102984 A102985 
               A102986
%K A102983 more,nonn
%O A102983 1,1
%A A102983 Robert G. Wilson v (rgwv(AT)rgwv.com), Dec 21 2004