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Number of ternary words of length n that are not "bifix-free".
2

%I #4 Mar 30 2012 16:49:56

%S 0,0,3,9,33,99,315,945,2883,8649,26091,78273,235233,705699,2118339,

%T 6355017,19068729,57206187,171629595,514888785,1544699313,4634097939,

%U 13902392691,41707178073,125121830427,375365491281

%N Number of ternary words of length n that are not "bifix-free".

%F Equals 3^n - A019308(n).

%Y See A019308 and A003000 for much more information. Cf. A094539.

%K nonn,easy

%O 0,3

%A _N. J. A. Sloane_, Jun 06 2004