Start with 1; for n>1, replace n by the concatenation of its prime factors in increasing order.
1, 2, 3, 22, 5, 23, 7, 222, 33, 25, 11, 223, 13, 27, 35, 2222, 17, 233, 19, 225, 37, 211
2 seqfan posts
Thu Apr 29 08:40:38 CEST 2010 [seqfan] Re: Concatenate prime factors of n