Saturday, January 16, 2021

My 1000th Leyland prime find

This evening I found my 1000th Leyland prime. My 500th was only ten months ago! The above chart extends the graph that I posted back then. I have 579 red values found using Mathematica (from 3 October 2015 to 3 July 2020), followed by 421 blue values found using xyyxsieve & pfgw64 (from 6 July 2020 on). I have it in mind that I might actually achieve 1500 finds by later this year. It's a tough target to reach because I'll be picking all the remaining low-hanging fruit (< 150000 decimal digits) in the ongoing search and I don't believe that there are quite 500 of those left.


  1. Hello Hans. We worked together over 40 years ago. It's great you are still involved working with prime numbers. Over the many years I have got so much enjoyment from the lovely wooden puzzle you gifted me when I was transferred to another location. After 35 years in the business working with you was one of my lasting memories.

    1. Although I've only ever gifted a handful of puzzles to fellow employees, I'm having difficulty attaching a name to you. 40 years is a long time! :)

    2. Hello Hans. It's Steve. I believe it was either Jane and Alliance store or Kipling and Dixon? The puzzle was out of 16 exotic wood pieces. The wood ranged from cherry, imbuyz, mulberry to oak and pzdovk. Anyway, I just felt I wanted to pass on how much your kind gesture meant to me and meeting people like you has enriched my life. Stay well and stay safe.

    3. Kipling and Dixon sounds about right. Thank you for your kind words.

    4. I think the puzzle might have been Stewart Coffin's "Cornucopia". If so, there would be a puzzle #, the initials STC, and a year on the tray — likely mid-1980s.