OFFSET
0,1
COMMENTS
1186061987030929990 is the largest of the first 126 numbers that require exactly 261 steps to turn into a palindrome (see A281506). 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)).
EXAMPLE
a(1) = 1186061987030929990 + 999290307891606811 = 2185352294922536801.
MATHEMATICA
NestList[#+IntegerReverse[#]&, 1186061987030929990, 20] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Jan 17 2019 *)
PROG
(Magma) k:=1186061987030929990; [n eq 1 select k else Self(n-1) + Seqint(Reverse(Intseq(Self(n-1)))): n in [1..20]]; // Bruno Berselli, Jan 23 2017
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Andrey S. Shchebetov and Sergei D. Shchebetov, Jan 23 2017
STATUS
approved