Lychrel Number

The first few numbers not known to produce palindromes when applying the 196-algorithm (i.e., a reverse-then-add sequence) are sometimes known as Lychrel numbers. This term was coined by VanLandingham in 2002 as a variation of his girlfriend Cheryl's name (VanLandingham, pers. comm., Jun. 9, 2005).

The first few Lychrel numbers are 196, 295, 394, 493, 592, 689, 691, 788, 790, 879, 887, ... (OEIS A023108). All Lychrel numbers with 17 or fewer digits are tabulated at https://www.p196.org/.

REFERENCES:

Sloane, N. J. A. Sequence A023108 in "The On-Line Encyclopedia of Integer Sequences."

VanLandingham, W. "196 and Other Lychrel Numbers." https://www.p196.org/.

VanLandingham, W. "Blackboard Archive." May 13, 2002. https://home.cfl.rr.com/p196/archive.html.