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%I #3 Mar 30 2012 17:40:23
%S 3,11,3,17,3,3,3,11,89,41,257,3,29,131,353,3,3,11,89,521,257,3,17,3,
%T 467,89,149,17,71,47,293,17,191,47,3,41,23,11,401,41,443,41,293,479,
%U 311,23,587,41,1289,1013,29,41,59,293,1031,17,23,17,347,401,599,11,227,827,401
%N Smallest prime prime(i) such that concatenation 2//0_(n)//prime(i) is prime.
%C We search for the prime such that the first prime (=2) concatenated with n zeros and concatenated with that prime is again a prime number.
%C If p = prime(i) is a d(i)-digit prime: q = 2 * 10^(n+d(i)) + p has to be prime.
%C Necessarily prime(i) is congruent to 2 (mod 3).
%C It is conjectured that prime(i) = 3 occurs infinitely often: at n= 0, 2, 4, 5, 6, 11, 15, 16, 21, 23, 34, 114, 119,...
%D E. I. Ignatjew, Mathematische Spielereien, Urania Verlag Leipzig/Jena/ Berlin 1982
%e n = 0: 2//3 = 23 = prime(9), 3 = prime(2) is first term
%e n = 1: 2//0//11 = 2011 = prime(305), 11 = prime(5) is 2nd term
%e n = 2: 2//00//3 = 2003 = prime(304), 3 = prime(2) is 3rd term
%Y Cf. A164968, A173291, A176316
%K base,nonn
%O 0,1
%A Eva-Maria Zschorn (e-m.zschorn(AT)zaschendorf.km3.de), Apr 26 2010
%E Offset corrected and sequence extended by _R. J. Mathar_, Apr 28 2010
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