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Amateur Quest For Lychrel Numbers

Posted by timothy on from the martin-gardner-would-be-proud dept.

Habberhead writes "Some people are aware of the quest for a palindromic solution for the number 196. Basically any number that doesn't form a palindrome by reversing and adding its digits is known as a Lychrel Number. (Sequence Number A023108 of Sloan's On-Line Encyclopedia of Integer Sequences) The number 196 happens to be the first of them. In over a year's worth of time, and more than 2 quadrillion calculations, this guy at www.p196.org has reversed and added the number over 100 MILLION times. His current answer is over 41 million digits long! Apparently he and a few others are also working on a distributed computing program for finding larger and larger Lychrel Numbers. It looks like they have in mind a Seti@Home style program with visible results."

5 of 310 comments (clear)

  1. Re:what? by cperciva · · Score: 5, Informative

    256 + 652 = 908
    908 + 809 = 1717
    1717 + 7171 = 8888, which is a palindrome.

    However,
    196 + 691 = 887
    887 + 788 = 1675
    1675 + 5761 = 7436
    7436 + 6347 = 13783
    and contining on for a few million digits still doesn't end up at a palindrome.

    --
    Tarsnap: Online backups for the truly paranoid
  2. In a nutshell.... by moniker_21 · · Score: 2, Informative

    Pick a number, any number. Reverse the digits in the number, add those reversed digits to the original number. Does this sum create a palindrome? If not, repeat the process with the new sum. By example:

    87+78 = 165
    165+651 = 726
    726+627 = 1353
    1353+3531 = 4884, a palindrome!

    This article is saying that for the thousands of numbers tested, every one except 196 has exhibited this property.

    --
    I posted to /. and all I got was this stupid sig
  3. Re:Simple Example by cperciva · · Score: 3, Informative

    I posted a story a week ago about the prime number problem being solved for the first time with a deterministic algorithm and it was rejected by /.

    You aren't talking about this by any chance, are you?

    --
    Tarsnap: Online backups for the truly paranoid
  4. It's not true, though. by dark-nl · · Score: 3, Informative

    879, 1997, and 7059 also have this property, whatever it is. The guy even explains this on his site. I wonder who he is, and why he doesn't put his name anywhere.

  5. Re:All the apathy here... by Prune · · Score: 2, Informative

    >> By definition the numbers 691, 887, 788, 1675, 5761, 7436, and 6347 must also have the same problem, since they're in the chain following 196.

    Read the article. These numbers don't count exactly because they follow in that chain. Only the seed of a chain counts.

    --
    "Politicians and diapers must be changed often, and for the same reason."