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Search: id:A143460
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| A143460 |
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Expansion of 1/(x^k*(1-x-3*x^(k+1))) for k=9. |
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+0
2
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| 1, 4, 7, 10, 13, 16, 19, 22, 25, 28, 31, 43, 64, 94, 133, 181, 238, 304, 379, 463, 556, 685, 877, 1159, 1558, 2101, 2815, 3727, 4864, 6253, 7921, 9976, 12607, 16084, 20758, 27061, 35506, 46687, 61279, 80038, 103801, 133729, 171550, 219802, 282076
(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 quaternary words with at least 9 0-digits between any other digits.
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FORMULA
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G.f.: 1/(x^9*(1-x-3*x^10)).
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MAPLE
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a := proc(k::nonnegint) local n, i, j; if k=0 then unapply (4^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 3 else 0 fi)^(n+k))[1, 1], n) fi end(9): seq (a(n), n=0..61);
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CROSSREFS
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9th column of A143461.
Sequence in context: A112335 A145289 A016777 this_sequence A143459 A143458 A004084
Adjacent sequences: A143457 A143458 A143459 this_sequence A143461 A143462 A143463
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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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