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Search: id:A045694
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| A045694 |
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Number of ternary words of length n (beginning with 0) with autocorrelation function 2^(n-1). |
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+0
2
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| 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; listen)
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OFFSET
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1,2
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FORMULA
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a(2n) = 3*a(2n-1) - a(n) for n >= 1; a(2n+1) = 3*a(2n) for n >= 1.
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MAPLE
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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); (Deutsch)
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CROSSREFS
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Equals A019308/3.
Sequence in context: A148444 A064190 A151281 this_sequence A129772 A046721 A151528
Adjacent sequences: A045691 A045692 A045693 this_sequence A045695 A045696 A045697
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KEYWORD
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nonn,easy
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AUTHOR
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TORSTEN.SILLKE(AT)LHSYSTEMS.COM
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EXTENSIONS
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More terms from Emeric Deutsch (deutsch(AT)duke.poly.edu), Aug 08 2005
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