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Search: id:A119749
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| A119749 |
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Number of compositions of n into odd blocks with one element in each block distinguished. |
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+0
1
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| 1, 1, 4, 7, 15, 32, 65, 137, 284, 591, 1231, 2560, 5329, 11089, 23076, 48023, 99935, 207968, 432785, 900633, 1874236, 3900319, 8116639, 16890880, 35150241, 73148321, 152223044, 316779047, 659223215, 1371856032, 2854858465
(list; graph; listen)
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OFFSET
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1,3
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REFERENCES
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Chen, R. and Shapiro, L., Preprint, 2006
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FORMULA
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G.f.: (x+x^3)/(x^4 - x^3 -2x^2 -x +1).
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EXAMPLE
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a(3) = 4 since Abc, aBc, abC come from one block of size 3 and A/B/C comes from having three blocks. The capital letters are the distinguished elements.
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MATHEMATICA
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Rest@ CoefficientList[ Series[x(1 + x^2)/(x^4 - x^3 - 2x^2 - x + 1), {x, 0, 50}], x] (* Robert G. Wilson v *)
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CROSSREFS
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Cf. A105309, A052530, A000045, A030267.
Sequence in context: A116969 A131090 A131935 this_sequence A145970 A145795 A065935
Adjacent sequences: A119746 A119747 A119748 this_sequence A119750 A119751 A119752
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KEYWORD
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easy,nonn
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AUTHOR
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Lou Shapiro (lshapiro(AT)howard.edu), Jul 30 2006
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EXTENSIONS
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More terms from Robert G. Wilson v (rgwv(AT)rgwv.com), Aug 01 2006
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