%I #11 Oct 01 2016 21:03:38
%S 1,1,2,1,2,1,1,1,1,2,1,2,1,1,1,1,2,1,2,1,2,1,2,1,2,1,1,1,1,2,1,2,1,1,
%T 1,1,2,1,2,1,2,1,2,1,2,1,1,1,1,2,1,2,1,1,1,1,2,1,2,1,1,1,1,2,1,2,1,1,
%U 1,1,2,1,2,1,1,1,1,2,1,2,1,2,1,2,1,2,1,1,1,1,2,1,2,1,1,1,1,2,1,2,1,2,1,2,1
%N Fixed point of the morphism 1 -> 1121211, 2 -> 1121212121211, starting from a(1) = 1.
%C Length of n-th run of identical symbols in A051069.
%H <a href="/index/Fi#FIXEDPOINTS">Index entries for sequences that are fixed points of mappings</a>
%F Sum_{k=1..n} a(k) = A007417(n).
%t Nest[ Function[ l, {Flatten[(l /. {1 -> {1, 1, 2, 1, 2, 1, 1}, 2 -> {1, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 1}})]}], {1}, 3] (* _Robert G. Wilson v_, Feb 26 2005 *)
%Y Cf. A007417, A051069.
%K easy,nonn
%O 1,3
%A _Philippe Deléham_, Mar 21 2004
%E More terms from _Robert G. Wilson v_, Feb 26 2005