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Search: id:A143447
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| A143447 |
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Expansion of 1/(x^k*(1-x-2*x^(k+1))) for k=4. |
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+0
2
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| 1, 3, 5, 7, 9, 11, 17, 27, 41, 59, 81, 115, 169, 251, 369, 531, 761, 1099, 1601, 2339, 3401, 4923, 7121, 10323, 15001, 21803, 31649, 45891, 66537, 96539, 140145, 203443, 295225, 428299, 621377, 901667, 1308553, 1899003, 2755601, 3998355, 5801689
(list; graph; listen)
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OFFSET
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0,2
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COMMENT
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a(n) is also the number of length n ternary words with at least 4 0-digits between any other digits.
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FORMULA
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G.f.: 1/(x^4*(1-x-2*x^5)).
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MAPLE
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a := proc(k::nonnegint) local n, i, j; if k=0 then unapply (3^n, n) else unapply ((Matrix(k+1, (i, j)-> if (i=j-1) or j=1 and i=1 then 1 elif j=1 and i=k+1 then 2 else 0 fi)^(n+k))[1, 1], n) fi end(4): seq (a(n), n=0..54);
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CROSSREFS
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4th column of A143453.
Sequence in context: A133848 A064076 A050842 this_sequence A152484 A071643 A039578
Adjacent sequences: A143444 A143445 A143446 this_sequence A143448 A143449 A143450
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KEYWORD
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nonn
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AUTHOR
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Alois P. Heinz (heinz(AT)hs-heilbronn.de), Aug 16 2008
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