%I A117831
%S A117831 1,1,40,7,0,0,39,6,0,0,38,5,0,18,37,3,0,43,10,0,4,42,9,4,4,41,7,0,47,40,
%T A117831 0,8,46,13,0,8,45,11,0,7,44,0,12,50,17,3,12,49,15,1,11,48,1,16,36,3,0,
               16,
%U A117831 35,1,0,41,8,2,2,40,7,2,2,39,5,0,45,12,0,6,44,11,0,6,43,9,0,49,42,0,10
%N A117831 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 A117831 It is conjectured that S_n always reaches a cycle.
%C A117831 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 (klaus-brockhaus(AT)t-online.de), 
               May 05 2006
%H A117831 N. J. A. Sloane, <a href="a117831.txt">Sequences of RADD type</a>
%Y A117831 S_1 is given in A117828, S_3 in A117829, S_1015 in A117807.
%Y A117831 Records are in A118473, A118474.
%Y A117831 Full list of sequences on this topic (1): A117230, A117521, A117800, 
               A117816, A117817, A117827, A117828, A117829, A117830, A117831 (this 
               sequence)
%Y A117831 Full list of sequences on this topic (2): A117837, A117841, A118473, 
               A118474, A118510, A118511, A118512, A118513, A118514, A118515, A118516
%Y A117831 Full list of sequences on this topic (3): A118517-A118533, A118535
%Y A117831 Sequence in context: A078084 A037937 A126652 this_sequence A152143 A033975 
               A033360
%Y A117831 Adjacent sequences: A117828 A117829 A117830 this_sequence A117832 A117833 
               A117834
%K A117831 nonn,base
%O A117831 1,3
%A A117831 N. J. A. Sloane (njas(AT)research.att.com), following discussions with 
               Luc Stevens, May 03 2006
%E A117831 Corrected and extended by Klaus Brockhaus, May 05 2006
%E A117831 Confirmed by N. J. A. Sloane (njas(AT)research.att.com), May 05 2006