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Starting with 1, smallest integer not yet in the sequence such that two neighboring digits of the sequence multiply to a prime.
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%I #15 Sep 14 2013 13:39:38

%S 1,2,12,13,15,17,121,3,131,5,151,7,171,21,31,51,71,212,1212,1213,1215,

%T 1217,1312,1313,1315,1317,1512,1513,1515,1517,1712,1713,1715,1717,

%U 12121,213,12131,215,12151,217,12171,312,13121,313,13131,315,13151,317,13171

%N Starting with 1, smallest integer not yet in the sequence such that two neighboring digits of the sequence multiply to a prime.

%K nonn,base

%O 1,2

%A _Eric Angelini_ and _Jim Nastos_, Apr 22 2012