Friday, February 06, 2015

(101*10^120072-87)/7 is prime

A good part of my dabbling in recreational arithmetic is searching for large primes. My previous best was 2*(10^39960+10^63+10^36+10^12)+2223 which has 39961 digits and dates to October 2011. Today I bettered that with (101*10^120072-87)/7 which is made up of 120074 digits — large enough to be on page three of Henri & Renaud Lifchitz's top probable prime records. The find arises out of an observation I made for A254005.
Posted by at

6 comments:

  1. UnknownFebruary 25, 2015 at 11:17 AM

    Hi,

    Are you the same person who had a site with old Scientific American covers at chesswanks-dot-com? The site went down a few weeks ago and I would like to know if it's coming back. I was a huge fan.

    Many thanks.

    ReplyDelete
  2. Hans HavermannFebruary 25, 2015 at 12:02 PM

    My SA weekly special-issue covers: http://chesswanks.com/pot/SAWSI/
    My SA monthly 1948-1987 covers: http://chesswanks.com/pot/SAC/

    If you are getting chesswanks.com, you should be getting the above.

    ReplyDelete
  3. UnknownFebruary 25, 2015 at 1:19 PM

    Many thanks for the quick reply. All of the following are down, for me and also according to http://www.downforeveryoneorjustme.com :

    chesswanks.com
    http://chesswanks.com/pot/SAWSI/
    http://chesswanks.com/pot/SAC/

    Also FYI, at the Wayback Machine (which archives more-or-less all websites everywhere, in case you're not familiar but I'm guessing you would be), the Scientific American pages don't work. The site shows up, but not the covers - instead of the images you see a generic image placeholder symbol.

    https://web.archive.org/web/20130617163242/http://chesswanks.com/pot/SAC/

    ReplyDelete
    Replies
    1. Hans HavermannFebruary 25, 2015 at 1:39 PM

      I can't fix the Wayback Machine but I think I fixed my domain access. Try those links again. I run my Personal Web Sharing through a router and if my LAN pointer changes (which it had) I need to re-direct it. I appreciate the heads-up.

      Delete
  4. UnknownFebruary 25, 2015 at 3:50 PM

    Yes they are all working now. Thanks very much.

    Do you have any other similar galleries? I'm not seeing anything at chesswanks.com. For that matter I don't see the SA galleries mentioned there at all. I stumbled on them directly somehow.

    (As for Wayback Machine, I tried asking in the forum why the images are missing from a simple basic site like your SA covers. However they have shut down their Wayback Machine forum entirely (refusing to explain why) so I had to post in another forum at archive.org. In general they're not helpful with user support so I don't expect much.)

    ReplyDelete
    Replies
    1. Hans HavermannFebruary 25, 2015 at 4:29 PM

      The weeklies covers derive from http://gladhoboexpress.blogspot.ca/2012/03/scientific-american-cover-art.html and the monthlies covers from http://chesswanks.com/blahg/odo/Blog/Entries/2010/9/30_Got_it_covered.html. No other galleries but I did link to a handful of other covers here: http://chesswanks.com/blahg/odo/Blog/Entries/2010/7/19_The_last_Scientific_American_weeklies.html.

      Delete

Subscribe to: Post Comments (Atom)