%I A088569
%S A088569 1,1,2,2,1,2,1,1,2,1,1,2,2,1,2,2,1,1,2,1,2,2,1,2,1,1,2,2,1,2,2,1,2,1,1,
%T A088569 2,1,1,2,2,1,2,1,1,2,1,2,2,1,2,2,1,1,2,1,1,2,2,1,2,1,1,2,1,1,2,2,1,2,2,
%U A088569 1,2,1,1,2,1,2,2,1,1,2,1,1,2,2,1,2,1,1,2,1,1,2,2,1,2,2,1,1,2,1,2,2,1,2
%N A088569 Anti-Kolakoski sequence (sequence of length runs never coincides with 
               the sequence itself).
%C A088569 Unique infinite word defined on alphabet {1,2} satisfying: a(1)=1, if 
               a(n)=2 length of n-th run is 1, if a(n)=1 length of n-th run is 2. 
               Kolakoski sequence satisfies the opposite definition : K(1)=1, if 
               K(n)=2 length of n-th run is 2, if K(n)=1 length of n-th run is 1.
%F A088569 a(n)=3-A000002(n+1)=A049705(n+1)
%e A088569 a(1)=1 hence first run must have length 2 and necessarily a(2)=1. Now 
               second run must have also length 2 and therefore a(3)=a(4)=2.
%Y A088569 Sequence in context: A164295 A035214 A071292 this_sequence A001285 A088424 
               A097456
%Y A088569 Adjacent sequences: A088566 A088567 A088568 this_sequence A088570 A088571 
               A088572
%K A088569 nonn
%O A088569 1,3
%A A088569 Benoit Cloitre (benoit7848c(AT)orange.fr), Nov 17 2003