Saturday, October 20, 2018

M from heaven

Some twenty months ago I posted a snippet of a probable-prime leaderboard and my #44 position in it. I was looking forward back then to reaching position #40. A month-and-a-half ago I had reached position #35, at which I was still yesterday when I grabbed this:

On October 8, Joerg Arndt received a personal message from an "M" that gave five large probable primes with the intent of removing from a specific OEIS sequence five of its terms. Joerg shared the post with the Sequence Fanatics Discussion list the next day. Now it's very unusual to have an OEIS sequence that removes terms as knowledge is advanced and by October 10, Neil Sloane (owner of the OEIS) killed that sequence because it was likely intended to be a duplicate of A076337 — but with additional (unproven) terms. What M did was show that five of those extra terms didn't in fact belong.

Also on October 10, I emailed M to let him/her know that the five probable primes were not yet in the probable prime records database. On Thursday (October 18), M (finally) replied that he/she had no desire to receive credit and that if I wanted to submit the results I should "feel free". So I rechecked the five numbers for probable primality and — this morning — submitted them. A couple of hours ago the database was updated:

That was quite the ascent! I should point out that Norbert Schneider at #28 is the only other person who — like me — has been actively looking for new Leyland primes. Of the thirteen currently largest-known examples, Norbert has contributed eight.

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