This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A045694 #8 Sep 04 2017 04:51:25 %S A045694 1,2,6,16,48,138,414,1226,3678,10986,32958,98736,296208,888210, %T A045694 2664630,7992664,23977992,71930298,215790894,647361696,1942085088, %U A045694 5826222306,17478666918,52435902018,157307706054,471922821954,1415768465862 %N A045694 Number of ternary words of length n (beginning with 0) with autocorrelation function 2^(n-1). %F A045694 a(2n) = 3*a(2n-1) - a(n) for n >= 1; a(2n+1) = 3*a(2n) for n >= 1. %p A045694 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 A045694 Equals A019308/3. %K A045694 nonn,easy %O A045694 1,2 %A A045694 TORSTEN.SILLKE(AT)LHSYSTEMS.COM %E A045694 More terms from _Emeric Deutsch_, Aug 08 2005