A089214 - OEIS

%I #5 Mar 30 2012 18:39:21

%S 1,3,2,4,2,4,1,3,2,4,1,3,1,3,2,4,2,4,1,3,1,3,2,4,1,3,2,4,2,4,1,3,2,4,

%T 1,3,1,3,2,4,1,3,2,4,2,4,1,3,1,3,2,4,2,4,1,3,2,4,1,3,1,3,2,4,2,4,1,3,

%U 1,3,2,4,1,3,2,4,2,4,1,3,1,3,2,4,2,4,1,3,2,4,1,3,1,3,2,4,1,3,2,4,2,4,1,3,2

%N Let u(1)=0, u(2)=1; for k>2, u(k)= A010060(k)*u(k-1) + u(k-2) (mod 2); then a(n)=4n-b(n) where sequence (b(k)) gives values such that u(b(k))=0.

%C A word on 4 letters built from Thue-Morse sequence.

%o (PARI) u=0;v=1;c=0;for(n=3,550,w=u%2+(subst(Pol(binary(n)),x,1)%2)*v;u=v;v=w;if(w==0,c++;print1(4*c-n,",")))

%K nonn

%O 1,2

%A _Benoit Cloitre_, Dec 09 2003