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%I #6 Oct 02 2013 15:12:45
%S 1,3,1,1,3,1,1,147,17,1,3,7,1,297,1
%N Smallest k>0 such that n*10^k + k is prime.
%C (a(n) mod 10) in {1,3,7,9}.
%C a(16), if it exists, is greater than 20000. - _Ryan Propper_, Jul 21 2006
%C a(16), if it exists, is greater than 42000. - _Ryan Propper_, Sep 25 2006
%Y a(floor(A030430(n)/10)) = 1.
%K nonn,more
%O 1,2
%A _Reinhard Zumkeller_, Mar 07 2005
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