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%I #14 Jul 08 2020 01:24:59
%S 0,0,1,0,0,1,0,0,1,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1,
%T 0,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1,
%U 0,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1,0
%N (001)(001)(001)(10)*.
%C Three copies of 001 followed by infinitely many copies of 10.
%C Lexicographically least binary sequence containing no subblock of the form S S reverse(S).
%H Colin Barker, <a href="/A272664/b272664.txt">Table of n, a(n) for n = 0..1000</a>
%H Jeffrey Shallit, <a href="https://cs.uwaterloo.ca/~shallit/Talks/acmes2.pdf">Experimental Combinatorics on Words Using the Walnut Prover</a>, Talk Presented at Computational Discovery in Mathematics (ACMES 2), University of Western Ontario, May 12 2016
%H <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (0,1).
%F From _Colin Barker_, May 16 2016: (Start)
%F a(n) = (1-(-1)^n)/2 for n>8.
%F a(n) = a(n-2) for n>10.
%F G.f.: x^2*(1+x^3-x^4)*(1-x^2+x^4) / ((1-x)*(1+x)).
%F (End)
%o (PARI) concat(vector(2), Vec(x^2*(1+x^3-x^4)*(1-x^2+x^4)/((1-x)*(1+x)) + O(x^50))) \\ _Colin Barker_, May 16 2016
%Y Cf. A241903.
%K nonn,easy
%O 0
%A _N. J. A. Sloane_, May 15 2016
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