Working in base 2, replace n by the concatenation of its prime divisors in increasing order (write answer in base 10).
1, 2, 3, 10, 5, 11, 7, 42, 15, 21, 11, 43, 13, 23, 29, 170, 17, 47, 19, 85, 31, 43, 23, 171
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Wed Jun 2 11:05:11 CEST 2010 [seqfan] Working in base 2, 3, k, replace n by the concatenation of its prime divisors in decreasing/increasing order (write answer in base 10) with or without multiplicity