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Search: id:A006980
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| 1, 2, 5, 12, 28, 64, 143, 315, 687, 1485, 3186, 6792, 14401, 30391, 63872, 133751, 279177, 581040, 1206151, 2497895, 5161982, 10646564, 21919161, 45052841, 92461171, 189489255, 387830160, 792810956, 1618840800, 3301999647
(list; graph; listen)
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OFFSET
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6,2
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REFERENCES
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N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
J. L. Yucas, Counting special sets of binary Lyndon words, Ars Combin., 31 (1991), 21-29.
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FORMULA
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G.f.: x^6 / ((1-x-x^2-x^3-x^4-x^5) * (1-x-x^2-x^3-x^4-x^5-x^6)). [From Alois P. Heinz (heinz(AT)hs-heilbronn.de), Oct 29 2008]
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MAPLE
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a:= n-> (Matrix(11, (i, j)-> if i=j-1 then 1 elif j=1 then [2, 1, 0, -1, -2, -4, -5, -4, -3, -2, -1][i] else 0 fi)^n) [1, 7]: seq (a(n), n=6..40); [From Alois P. Heinz (heinz(AT)hs-heilbronn.de), Oct 29 2008]
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CROSSREFS
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Sequence in context: A111586 A006979 A019301 this_sequence A045623 A001410 A019486
Adjacent sequences: A006977 A006978 A006979 this_sequence A006981 A006982 A006983
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KEYWORD
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nonn
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AUTHOR
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Simon Plouffe (simon.plouffe(AT)gmail.com)
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EXTENSIONS
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More terms and better definition from Alois P. Heinz (heinz(AT)hs-heilbronn.de), Oct 29 2008
Corrected definition: 6th column of A048004. - Geoffrey Critzer (critzer.geoffrey(AT)usd443.org), Nov 09 2008
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