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a(1) = 1; for n>1, a(n) = least k such that concatenation of n copies of k with all previous concatenations gives a prime.
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%I #4 Dec 05 2013 19:57:05

%S 1,9,7,3,29,19,21,121,7,211,207,11,221,347,99,123,303,189,1131,1179,

%T 2069,3437,2211,211,3169,1551,3493,7433,6939,1053,1537,9417,4491,1257,

%U 19693,9,1653,3329,317,8667,799,1053,5617,6049,1721,24871,2751,737,3303,29079

%N a(1) = 1; for n>1, a(n) = least k such that concatenation of n copies of k with all previous concatenations gives a prime.

%e 199, 199777, 1997773333, 19977733332929292929 are all primes.

%Y Cf. A111472.

%K base,nonn

%O 1,2

%A _Amarnath Murthy_, Aug 05 2005

%E More terms from _Donovan Johnson_, Feb 26 2008