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A045694 Number of ternary words of length n (beginning with 0) with autocorrelation function 2^(n-1). 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 (list; graph; refs; listen; history; text; internal format)
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 A046721

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

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Last modified October 22 06:02 EDT 2018. Contains 316432 sequences. (Running on oeis4.)