OFFSET
0,1
COMMENTS
1999291987030606810 is the largest of the 126 presently known numbers that require exactly 261 steps to turn into a palindrome (see A281508). It is also the largest discovered "most delayed palindrome". The sequence reaches a 119-digit palindrome after 261 steps (see b-file). The number was obtained empirically using computer algorithms and was not reported before.
REFERENCES
Popular Computing (Calabasas, CA), The 196 Problem, Vol. 3 (No. 30, Sep 1975).
LINKS
Sergei D. Shchebetov, Table of n, a(n) for n = 0..261
Jason Doucette, World Records
Yutaka Nishiyama, Numerical Palindromes and the 196 Problem, International Journal of Pure and Applied Mathematics, Volume 80 No. 3 2012, 375-384.
R. Styer, The Palindromic Conjecture and the Fibonacci Sequence, Villanova University, 1986, 1-11.
C. W. Trigg, Palindromes by Addition, Mathematics Magazine, 40 (1967), 26-28.
C. W. Trigg, More on Palindromes by Reversal-Addition, Mathematics Magazine, 45 (1972), 184-186.
Wikipedia, Lychrel Number
196 and Other Lychrel Numbers, 196 and Lychrel Number
FORMULA
a(n+1) = a(n) + rev(a(n)).
a(n) = A281507(n) for n>0. - R. J. Mathar, Jan 27 2017
EXAMPLE
a(1) = 1999291987030606810 + 186060307891929991 = 2185352294922536801.
CROSSREFS
KEYWORD
nonn,base,less
AUTHOR
Andrey S. Shchebetov and Sergei D. Shchebetov, Jan 24 2017
STATUS
approved