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Search: id:A005328
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| A005328 |
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Certain subgraphs of a directed graph.
(Formerly M3118)
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+0
1
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| 1, 3, 28, 510, 18631, 1351413, 194192398, 55272612720, 31184369778961, 34909296450535023, 77616063417393956368, 343049603717222441078130, 3016429354620114423122804491, 52801416275268069417410827891833
(list; graph; listen)
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OFFSET
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2,2
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REFERENCES
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N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
Andresen, E.; Kjeldsen, K.; On certain subgraphs of a complete transitively directed graph. Discrete Math. 14 (1976), no. 2, 103-119.
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FORMULA
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a(n)=p(n-1)*sum((-1)^j*(n-1-j)/p(j), j=0..n-2), where p(0)=1, p(k)=product(2^i-1, i=1..k) for k>0. - Emeric Deutsch (deutsch(AT)duke.poly.edu), Jan 23 2005
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MAPLE
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p:=proc(n) if n=0 then 1 else product(2^i-1, i=1..n) fi end: a:=n->p(n-1)*sum((-1)^j*(n-1-j)/p(j), j=0..n-2): seq(a(n), n=2..17); (Deutsch)
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CROSSREFS
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Sequence in context: A060545 A108288 A058804 this_sequence A161971 A156315 A062497
Adjacent sequences: A005325 A005326 A005327 this_sequence A005329 A005330 A005331
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KEYWORD
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nonn
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AUTHOR
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N. J. A. Sloane (njas(AT)research.att.com).
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EXTENSIONS
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More terms from Emeric Deutsch (deutsch(AT)duke.poly.edu), Jan 23 2005
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