Search: id:A089675
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%I A089675
%S A089675 1,2,3,17,140,990,1887,3530,5996,13820,21873,26045
%N A089675 Numbers n such that 9*R_n - 2 is a prime number, where R_n = 11...1 is 
               the repunit (A002275) of length n.
%C A089675 Also numbers n such that 10^n - 3 is a (probable) prime number.
%C A089675 Next term is greater than 26045. - Patrick De Geest (pdg(AT)worldofnumbers.com, 
               Dec 28 2004.
%C A089675 If n is in the sequence (10^n-3 is prime) and m=3*(10^n-3) then phi(m)=reversal(m)(m 
               is in the sequence A069215). - Farideh Firoozbakht (mymontain(AT)yahoo.com), 
               Dec 25 2004.
%H A089675 <a href="Sindx_Pri.html#Pri_rep">Index entries for primes involving repunits</
               a>
%e A089675 10^2 - 3 = 97 is a prime number (in fact all are the largest less than 
               10^n).
%t A089675 To check for all n up to m: For[n=1, n<m, If[PrimeQ[10^n-3]==True, Print[n]];
               n++ ]
%Y A089675 Cf. A069215, A101700.
%Y A089675 Sequence in context: A135726 A164816 A042978 this_sequence A041383 A042903 
               A132534
%Y A089675 Adjacent sequences: A089672 A089673 A089674 this_sequence A089676 A089677 
               A089678
%K A089675 more,nonn
%O A089675 1,2
%A A089675 Michael Gottlieb (mzrg(AT)verizon.net), Jan 05 2004.
%E A089675 a(8) from Robert G. Wilson v, Jan 14 2004.
%E A089675 a(9) and a(10) from Gabriel Cunningham (gcasey(AT)mit.edu), Mar 06 2004.
%E A089675 a(11) from Gabriel Cunningham (gcasey(AT)mit.edu), Mar 13 2004.
%E A089675 a(12) from Henri Lifchitz (HLifchitz(AT)compuserve.com).
%E A089675 Edited by Patrick De Geest (pdg(AT)worldofnumbers.com), Dec 28 2004.

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