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Search: id:A119915
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| A119915 |
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Number of ternary words of length n and having exactly one run of 0's of odd length. |
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+0
2
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| 0, 1, 4, 13, 40, 117, 332, 921, 2512, 6761, 18004, 47525, 124536, 324317, 840092, 2166065, 5562272, 14232273, 36300196, 92321085, 234192584, 592695109, 1496810732, 3772761289, 9492450672, 23844342073, 59804611060, 149787196117
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OFFSET
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0,3
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COMMENT
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Column 1 of A119914.
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FORMULA
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G.f.= z(1-z^2)/(1-2z-z^2)^2.
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EXAMPLE
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a(3)=13 because we have 000, 011, 012, 021, 022, 101, 102, 110, 120, 201, 202, 210, and 220 (for example, 001, 020 do not qualify).
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MAPLE
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g:=z*(1-z^2)/(1-2*z-z^2)^2: gser:=series(g, z=0, 34): seq(coeff(gser, z, n), n=0..30);
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CROSSREFS
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Cf. A119914.
Sequence in context: A121192 A133409 A000746 this_sequence A137744 A027130 A027121
Adjacent sequences: A119912 A119913 A119914 this_sequence A119916 A119917 A119918
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KEYWORD
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nonn
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AUTHOR
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Emeric Deutsch (deutsch(AT)duke.poly.edu), May 29 2006
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