Editing Lychrel number (section)

==196 palindrome quest==
Because [[196 (number)|196]] ([[base-10]]) is the smallest candidate Lychrel number, it has received the most attention.

In the 1980s, the 196 palindrome problem attracted the attention of [[microcomputer]] hobbyists, with search programs by [[Jim Butterfield]] and others appearing in several mass-market computing magazines.<ref name="transactor406">{{cite journal
  |author=<!-- Staff writer; no byline -->
  |year=1984
  |title=Bits and Pieces
  |journal=[[The Transactor]]
  |publisher=[[Transactor Publishing]]
  |volume=4
  |issue=6
  |pages=16–23
  |url=https://archive.org/details/transactor-magazines-v4-i06
  |access-date=26 December 2014
}}</ref><ref name="ahoy1984">{{cite journal |last=Rupert |first=Dale |date=October 1984 |title=Commodares: Programming Challenges |publisher=Ion International |journal=[[Ahoy!]] |number=10 |pages=23, 97–98 |url=https://archive.org/details/ahoy-magazine-10}}</ref><ref name="ahoy1985">{{cite journal |last=Rupert |first=Dale |date=June 1985 |title=Commodares: Programming Challenges |journal=[[Ahoy!]] |publisher=Ion International |number=18 |pages=81–84,114 |url=https://archive.org/details/ahoy-magazine-18}}</ref> In 1985 a program by James Killman ran unsuccessfully for over 28 days, cycling through 12,954 passes and reaching a 5366-digit number.<ref name="ahoy1985" />

[[John Walker (programmer)|John Walker]] began his 196 Palindrome Quest on 12 August 1987 on a [[Sun Microsystems|Sun]] 3/260 workstation. He wrote a [[C (programming language)|C]] program to perform the reversal and addition iterations and to check for a palindrome after each step. The program ran in the [[background (computer software)|background]] with a low priority and produced a checkpoint to a file every two hours and when the system was shut down, recording the number reached so far and the number of iterations. It restarted itself automatically from the last checkpoint after every shutdown. It ran for almost three years, then terminated (as instructed) on 24 May 1990 with the message:
:Stop point reached on pass 2,415,836.
:Number contains 1,000,000 digits.
The sequence starting with 196 had grown to a number of one million digits after 2,415,836 iterations without reaching a palindrome. Walker published his findings on the internet along with the last checkpoint, inviting others to resume the quest using the number reached so far.

In 1995, Tim Irvin and Larry Simkins used a [[Multiprocessing|multiprocessor]] computer and reached the two million digit mark in only three months without finding a palindrome. Jason Doucette then followed suit and reached 12.5 million digits in May 2000. Wade VanLandingham used Jason Doucette's program to reach 13 million digits, a record published in Yes Mag: Canada's Science Magazine for Kids. Since June 2000, Wade VanLandingham has been carrying the flag using programs written by various enthusiasts. By 1 May 2006, VanLandingham had reached the 300 million digit mark (at a rate of one million digits every 5 to 7 days). Using [[distributed processing]],<ref>{{cite conference |last1=Swierczewski |first1=Lukasz |last2=Dolbeau |first2=Romain |date=June 23, 2014 |title=The p196_mpi Implementation of the Reverse-And-Add Algorithm for the Palindrome Quest |conference=[[International Supercomputing Conference]] |location=[[Leipzig, Germany]] |url=http://www.isc-events.com/isc14_ap/presentationdetails.htm?t=presentation&o=264&a=select&ra=sessiondetails |access-date=June 11, 2014 |archive-date=April 19, 2015 |archive-url=https://web.archive.org/web/20150419100449/http://www.isc-events.com/isc14_ap/presentationdetails.htm?t=presentation&o=264&a=select&ra=sessiondetails |url-status=dead }}</ref> in 2011 Romain Dolbeau completed a billion iterations to produce a number with 413,930,770 digits, and in February 2015 his calculations reached a number with a billion digits.<ref>{{cite web |last=Dolbeau |first=Romain |author-link=Romain Dolbeau |title=The p196_mpi page |website=www.dolbeau.name |url=http://www.dolbeau.name/dolbeau/p196/p196.html |archive-url=https://web.archive.org/web/20161020091408/http://www.dolbeau.name/dolbeau/p196/p196.html |archive-date=20 October 2016}}</ref> A palindrome has yet to be found.

Other potential Lychrel numbers which have also been subjected to the same brute force method of repeated reversal addition include 879, 1997 and 7059: they have been taken to several million iterations with no palindrome being found.<ref>{{cite web |title=Lychrel Records |url=http://home.cfl.rr.com/p196/lychrel+records.html |access-date=September 2, 2016 |archive-date=October 21, 2006 |archive-url=https://web.archive.org/web/20061021025636/http://home.cfl.rr.com/p196/lychrel+records.html |url-status=dead }}</ref>