%I #7 Jul 19 2022 14:58:52
%S 1,0,0,1,1,1,1,1,1,0,0,1,1,0,0,1,1,0,0,1,1,0,0,1,1,0,0,1,1,0,0,1,1,1,
%T 1,1,1,0,0,1,1,0,0,1,1,1,1,1,1,0,0,1,1,0,0,1,1,1,1,1,1,0,0,1,1,0,0,1,
%U 1,1,1,1,1,0,0,1,1,0,0,1,1,1,1,1,1,0
%N Fixed point of the morphism 0->11, 1->1001.
%H Clark Kimberling, <a href="/A285621/b285621.txt">Table of n, a(n) for n = 1..10000</a>
%H <a href="/index/Fi#FIXEDPOINTS">Index entries for sequences that are fixed points of mappings</a>
%e 0 -> 11 -> 10011001 -> 100111111001100111111001 -> 10011111100110011001100110011001... ->
%t s = Nest[Flatten[# /. {0 -> {1, 1}, 1 -> {1, 0, 0, 1}}] &, {0}, 10] (* A285621 *)
%t Flatten[Position[s, 0]] (* A285622 *)
%t Flatten[Position[s, 1]] (* A285623 *)
%t SubstitutionSystem[{0->{1,1},1->{1,0,0,1}},{1},{5}][[1]] (* _Harvey P. Dale_, Jul 19 2022 *)
%Y Cf. A285622, A285623, A285625.
%K nonn,easy
%O 1
%A _Clark Kimberling_, May 01 2017