%I A122497
%S A122497 1,2,1,1,2,2,1,2,1,1,2,1,2,2,1,1,2,2,1,2,1,1,2,2,1,1,2,1,2,2,1,2,1,1,2,
%T A122497 1,2,2,1,1,2,2,1,2,1,1,2,1,2,2,1,2,1,1,2,2,1,1,2,1,2,2,1,1,2,2,1,2,1,1,
%U A122497 2,2,1,1,2,1,2,2,1,2,1,1,2,1,2,2,1,1,2,2,1,2,1,1,2,2,1,1,2,1,2,2,1,1,2
%N A122497 Let f(S) denote the interchange of 1's and 2's in S. Let S_0 = 1, S_{N+1} 
               = f(S_N).S_N, where the dot indicates concatenation. Sequence gives 
               S_0.S_1.S_2.S_3....
%C A122497 An alternating triangular Morse -Thue sequence based on A010060 using 
               {1,2} instead of {0,1} substitutions.
%H A122497 Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/
               Thue-MorseConstant.html">Thue-Morse Constant</a>
%F A122497 1->)1,2} 2->{2,1} a(n) = ThueMorse[n, 1 + Mod[n, 2]]
%e A122497 The first few S_i are:
%e A122497 1
%e A122497 2, 1
%e A122497 1, 2, 2, 1
%e A122497 2, 1, 1, 2, 1, 2, 2, 1
%e A122497 1, 2, 2, 1, 2, 1, 1, 2, 2, 1, 1, 2, 1, 2, 2, 1
%t A122497 ThueMorse[n_, b_] := Nest[Flatten[ # /. {1 -> {1, 2}, 2 -> {2, 1}}] &, 
               {b}, n] a = Table[ThueMorse[n, 1 + Mod[n, 2]], {n, 0, 7}] Flatten[a]
%Y A122497 Cf. A010060, A014571, A014572, A074072, A074073.
%Y A122497 Sequence in context: A049705 A060236 A006345 this_sequence A154402 A023396 
               A091221
%Y A122497 Adjacent sequences: A122494 A122495 A122496 this_sequence A122498 A122499 
               A122500
%K A122497 nonn
%O A122497 1,2
%A A122497 Roger Bagula (rlbagulatftn(AT)yahoo.com), Sep 15 2006
%E A122497 Edited by N. J. A. Sloane (njas(AT)research.att.com), May 22 2007