[seqfan] The Wichita Algorithm.
rgwv at rgwv.com
Fri Jul 29 22:39:17 CEST 2022
We know how to navigate down the Wichita Tree using the mapping k -> k - k/p, where p is any prime divisor of k. But do you know how to navigate up the tree?
Say you have a leaf or node, 20, it flows towards the root of the tree, 1, through 10 (20-20/2) or 16 (20-20/5). But what numbers flow from above into 20. See my comment in A067513.
So using this information, instead of testing all numbers less than or equal to 2^n to see if they belong to a particular row or rung of A334111, we only need to know the members of the previous rung and construct it.
However; by the time you get to the 40th rung, you will have used up 64 Gig of ram. Therefore I only take the first 10 million terms. I started with 150,000 but quickly realized that was too small. Next I tried 250,000. That is what I submitted for A105017. I then used 1 million terms and I found just 2 errors in the first 200 terms. So now I am using 10 million terms, but it is extremely slow as you can imagine.
Sequentially yours, Bob.
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