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A Thue-Morse-Stern sequence.
3

%I #3 Mar 30 2012 18:59:02

%S 0,0,1,0,2,1,2,0,0,2,1,1,1,2,0,0,1,0,0,2,1,1,0,1,0,1,1,2,0,0,1,0,2,1,

%T 2,0,1,0,0,2,1,1,0,1,2,0,2,1,2,0,2,1,0,1,1,2,0,0,1,0,2,1,2,0,0,2,1,1,

%U 1,2,0,0,2,1,2,0,1,0,0,2,1,1,0,1,2,0,2,1,1,2,0,0,0,2,1,1,1,2,0,0,0

%N A Thue-Morse-Stern sequence.

%C a(2n+1) = a(n).

%F a(n)=mod(-1+sum{k=0..floor(n/2), mod(binomial(n-k, k), 2)}, 3); a(n)=mod(-1+A002487(n+1), 3).

%Y Cf. A010060.

%K easy,nonn

%O 0,5

%A _Paul Barry_, Dec 10 2004