Starting with 2, successively concatenate the numbers in the prime factorization of a(n-1), including both the prime and its exponent.
2, 21, 3171, 31711511, 131171431471711, 16333180310678671
1 seqfan posts
Thu Sep 15 02:15:02 CEST 2011 [seqfan] Re: Do 20 and 105 eventually reach a prime in these sequences?