A045694 Number of ternary words of length n (beginning with 0) with autocorrelation function 2^(n-1).

1, 2, 6, 16, 48, 138, 414, 1226, 3678, 10986, 32958, 98736, 296208, 888210, 2664630, 7992664, 23977992, 71930298, 215790894, 647361696, 1942085088, 5826222306, 17478666918, 52435902018, 157307706054, 471922821954, 1415768465862

Offset

1,2

Links

Table of n, a(n) for n=1..27.

Formula

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

Maple

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

Crossrefs

Equals A019308/3.

Sequence in context: A148444 A064190 A151281 * A225178 A129772 A360856

Adjacent sequences: A045691 A045692 A045693 * A045695 A045696 A045697

Keyword

nonn,easy

Author

TORSTEN.SILLKE(AT)LHSYSTEMS.COM

Extensions

More terms from Emeric Deutsch, Aug 08 2005

Status

approved