[oh_sigh]

Those are the necessary pre and post processing steps that you need to compute outside of the FRACTRAN system for the fibonacci example from the article.

If you could do those steps the entire process would be self contained, which you should be able to if the claim of yielding all possible computations is correct.

(actually, it is log2(x) that would need to be implemented and not 2^x, but my point remains).

[anonymoushn]

One reasonable design equivalent to FRACTRAN is to do away with the divisibility checks and store an array of counts of prime factors. Then you could put the input in the 5s slot and read the output from the 2s slot without computing the values of these expressions.