MC: Ping-Pong Cubes

[Joe Horn]

(06-20-2018 09:30 PM)Valentin Albillo Wrote:  ...
- A few hours later I saw the MC and posted a 5-line program for the HP-71B which finds all 10 small solutions in 0.49 sec. I naively expected some comment by Mr. Horn, as my code includes a novel technique to check non-iteratively whether a number is a PPN or not, and also because Mr. Horn hosted in the very distant past a column called "The Titan File" dedicated to the HP-71B so I thought he would appreciate my solution all the more. Alas, Mr. Horn didn't see it fit to comment anything and he didn't post even simply to acknowledge he had read my solution either.

- Nevertheless (and as this is not the first time Mr. Horn ignores my solutions to one of his challenges)...

...
- Thus, two weeks after posting my 71B solution, I posted a 100+ line message with tables, the formulas which generated them (in HP-71B BASIC), an explanation of the techniques used, comments and conclusions, the most important being that except for the 10 small ones already known there is no PPN less than 10^20 that generates a PPC when cubed, so any further search should necessarily begin with PPN candidates at least 21-digit long.

- Again, I naively thought that Mr. Horn would appreciate my original research and so would post some comment or at least would acknowledge this time that he had read it, but it was not to be, he completely ignored it. Again.

...
- To my utter surprise, Mr. Horn then went on and while he didn't ever reply to either my 71B solution or my extensive original research, he did immediately reply to Warbucks post, telling him that "that" (i.e., posting a 21-digit solution) "would be greatly appreciated."

YIKES! Sorry! YES, I didn't reply, but NO, I was NOT ignoring your posts! You were clearly WAY ahead of me regarding this MC, so I thought it prudent to stay out of your way. I'm very grateful for your postings (ALL of them, going back many many years!), and I'm very sorry if saying this NOW is too little too late to prevent you from feeling offended by my silence.

(06-20-2018 09:30 PM)Valentin Albillo Wrote:  To end on a realistic note and contingent on there being some interest, in a few days I'll post updated details extracted from my Original Research, establishing new, improved lower bounds and commenting on several heuristics I've thoroughly researched and the conclusions that can be extracted from them. Oh, and last-but-not-least a quite solvable PPN/PPC-based counter-MC for Mr. Horn and interested readers (including Warbucks).

Yes, I'm interested. Thanks in advance.