%N Let S_n be the infinite sequence formed by starting with n and repeatedly reversing the digits and adding 4 to get the next term. Sequence gives number of steps for S_n to reach a cycle, or -1 if no cycle is ever reached.
%C It is conjectured that S_n always reaches a cycle.
%C There are 22 different cycles of length 90 with 4-digit components. I guess that at most half of the numbers between 1000 and 10000 lead to the cycle of length 54 shown in A117830. - _Klaus Brockhaus_, May 05 2006
%H N. J. A. Sloane and others, <a href="/wiki/Sequences_of_RADD_type">Sequences of RADD type</a>, OEIS wiki.
%Y S_1 is given in A117828, S_3 in A117829, S_1015 in A117807.
%Y Records are in A118473, A118474.
%Y Full list of sequences on this topic (1): A117230, A117521, A117800, A117816, A117817, A117827, A117828, A117829, A117830, A117831 (this sequence)
%Y Full list of sequences on this topic (2): A117837, A117841, A118473, A118474, A118510, A118511, A118512, A118513, A118514, A118515, A118516
%Y Full list of sequences on this topic (3): A118517-A118533, A118535
%A _N. J. A. Sloane_, following discussions with Luc Stevens, May 03 2006
%E Corrected and extended by Klaus Brockhaus, May 05 2006
%E Confirmed by _N. J. A. Sloane_, May 05 2006