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Search: id:A007649
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| A007649 |
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Number of set-like molecular species of degree n.
(Formerly M0824)
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+0
2
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| 1, 1, 2, 3, 7, 9, 20, 26, 54, 74, 137, 184, 356, 473, 841, 1154, 2034, 2742, 4740, 6405, 10874, 14794, 24515, 33246, 54955, 74380, 120501, 163828, 263144, 356621, 567330, 768854, 1212354, 1644335, 2567636, 3478873
(list; graph; listen)
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OFFSET
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0,3
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COMMENT
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A set-like molecular species is formed from the species of sets, E, through species addition, product and substitution.
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REFERENCES
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G. Labelle and P. Leroux, Identities and enumeration: weighting connected components, Abstracts Amer. Math. Soc., 15 (1994), Meeting #896.
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
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LINKS
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G. Labelle and P. Leroux, An extension of the exponential formula in enumerative combinatorics
N. J. A. Sloane, Transforms
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FORMULA
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Euler Transform of A007650. Define c(n): c(0)=0. c(k)=a(k), k>0. A007650=MOEBIUSi(c)-c. (Christian G. Bower (bowerc(AT)usa.net), Feb 23 2006)
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CROSSREFS
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Cf. A000638, A007650.
Sequence in context: A075855 A140189 A165803 this_sequence A046152 A057239 A024541
Adjacent sequences: A007646 A007647 A007648 this_sequence A007650 A007651 A007652
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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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