%I A102423
%S A102423 1,1,1,1,1,1,1,17,17,17,1,1,1,17,1,1,1,1,1,1,1,17,1,1,1,1,1,1,1,1,17,1,
%T A102423 1,1,17,1,1,17,17,1,1,1,1,1,1,1,1,17,17,1,1,1,1,17,17,1,1,1,1,1,17,17,
               1,
%U A102423 1,1,1,1,17,17,1,1,1,1,1,1,1,17,1,1,1,1,1,1,1,17,17,17,1,1,1,1,1,1,1,1
%N A102423 Start at 2n+1, iterate the map x -> A102421(x); sequence gives smallest 
               number in resulting cycle, or -1 if the trajectory never cycles.
%C A102423 See A102421 for further comments.
%t A102423 nextx[x_Integer] := Block[{a = x}, a = 3a + 1; While[EvenQ@a, a /= 2]; 
               a = 3a - 1; While[EvenQ@a, a /= 2]; a]; f[n_] := NestWhile[nextx, 
               n, MemberQ[{1, 17, 19, 43, 97, 109}, # ] &]; Table[ If[ f[2n + 1] 
               == 1, 1, 17], {n, 0, 94}] (* Robert G. Wilson v Sep 20 2006 *)
%Y A102423 Sequence in context: A004458 A082123 A050256 this_sequence A010856 A060360 
               A081702
%Y A102423 Adjacent sequences: A102420 A102421 A102422 this_sequence A102424 A102425 
               A102426
%K A102423 nonn
%O A102423 0,8
%A A102423 N. J. A. Sloane (njas(AT)research.att.com), based on email from Dan Asimov 
               (dasimov(AT)earthlink.net), Sep 15 2006
%E A102423 More terms from Robert G. Wilson v Sep 20 2006