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%I #9 Jul 31 2024 11:04:40
%S 1,3,7,73,433,607,13381,37279,4800307,1281054613,63338216281
%N a(1) = 1, a(n) = smallest number > a(n-1) such that concatenation a(k) a(n) is prime for all k = 1 to n-1. Stop if no such number exists.
%C The sequence is probably finite.
%e a(5)=433 since 1433, 3433, 7433 and 73433 are all primes and for every 73<x<433, at least one of 1x, 3x, 7x, 73x is not prime.
%K base,more,nonn
%O 1,2
%A _Amarnath Murthy_, Sep 28 2002
%E Corrected and extended by _Giovanni Resta_, Jun 18 2003
%E a(11) from _Michael S. Branicky_, Jul 31 2024