In base ten, no Lychrel numbers have been yet proven to exist, but many, including 196, are suspected on heuristic[1] and statistical grounds.
The name "Lychrel" was coined by Wade Van Landingham as a rough anagram of "Cheryl", his girlfriend's first name.
All one-digit and two-digit numbers eventually become palindromes after repeated reversal and addition.
Computer programs by Jason Doucette, Ian Peters and Benjamin Despres have found other Lychrel candidates.
Indeed, Benjamin Despres' program has identified all suspected Lychrel seed numbers of less than 17 digits.
[5] The brute-force method originally deployed by John Walker has been refined to take advantage of iteration behaviours.
The term thread, coined by Jason Doucette, refers to the sequence of numbers that may or may not lead to a palindrome through the reverse and add process.
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.
[7][8][9] In 1985 a program by James Killman ran unsuccessfully for over 28 days, cycling through 12,954 passes and reaching a 5366-digit number.
[9] John Walker began his 196 Palindrome Quest on 12 August 1987 on a Sun 3/260 workstation.
He wrote a C program to perform the reversal and addition iterations and to check for a palindrome after each step.
It ran for almost three years, then terminated (as instructed) on 24 May 1990 with the message: 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 multiprocessor computer and reached the two million digit mark in only three months without finding a palindrome.
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.
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.
In fact, in any given base b, no single-digit number takes more than two iterations to form a palindrome.