%I #16 Jan 02 2024 21:09:32
%S 2,1,2,2,1,2,1,1,2,2,1,2,2,1,1,2,1,1,2,1,2,2,1,1,2,1,1,2,2,1,2,1,1,2,
%T 1,1,2,2,1,2,2,1,2,1,1,2,1,2,2,1,1,2,1,1,2,1,2,2,1,2,2,1,1,2,1,2,2,1,
%U 2,1,1,2,1,1,2,2,1,2,2,1,2,1,1,2,2,1,2,2,1,1,2,1,2,2,1,2,1,1,2,1,1,2,2,1,2,2,1,1,2,1,2
%N Unique sequence a of 1's and 2's such that a(1) = 2 and r(r(a)) = a != r(a), where for any sequence s, r(s) is the sequence of lengths of runs of same symbols in s; r(a) is sequence A025142.
%D C. Kimberling, Problem 90: Runlength sequences, Mathematische Semesterberichte, 44 (1997) 9495.
%Y Cf. A025142.
%Y Differs from A014675 in many entries starting at entry 8.
%Y Cf. A078880 (satisfies s = r(s)), A288724 (satisfies s = r(r(r(s)))).
%K nonn
%O 1,1
%A _Clark Kimberling_
