A045694 - OEIS

%I #8 Sep 04 2017 04:51:25

%S 1,2,6,16,48,138,414,1226,3678,10986,32958,98736,296208,888210,

%T 2664630,7992664,23977992,71930298,215790894,647361696,1942085088,

%U 5826222306,17478666918,52435902018,157307706054,471922821954,1415768465862

%N Number of ternary words of length n (beginning with 0) with autocorrelation function 2^(n-1).

%F a(2n) = 3*a(2n-1) - a(n) for n >= 1; a(2n+1) = 3*a(2n) for n >= 1.

%p a:=proc(n) if n=1 then 1 elif n mod 2 = 0 then 3*a(n-1)-a(n/2) else 3*a(n-1) fi end: seq(a(n),n=1..31); # _Emeric Deutsch_, Aug 08 2005

%Y Equals A019308/3.

%K nonn,easy

%O 1,2

%A TORSTEN.SILLKE(AT)LHSYSTEMS.COM

%E More terms from _Emeric Deutsch_, Aug 08 2005