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A058880
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Number of orientations of an n-cycle.
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1
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12, 36, 104, 352, 1172, 4119, 14572, 52492, 190652, 699266, 2581112, 9587602, 35791472, 134219859, 505290272, 1908881998, 7233629132, 27487817244, 104715393912, 399822505942, 1529755308212, 5864062368274, 22517998136936
(list; graph; refs; listen; history; internal format)
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OFFSET
| 3,1
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REFERENCES
| F. Harary and E. M. Palmer, Graphical Enumeration, Academic Press, NY, 1973, p. 129, (5.3.3).
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MAPLE
| A058880 := proc(n) local d, t1, t2; if n mod 2 = 0 then t1 := 2^((n-4)/2) else t1 := 0; fi; t2 := divisors(n); for d in t2 do t1 := t1+phi(d)*2^(2*n/d)/(2*n); od; t1; end;
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CROSSREFS
| Sequence in context: A172218 A172212 A060621 * A055551 A073403 A064518
Adjacent sequences: A058877 A058878 A058879 * A058881 A058882 A058883
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KEYWORD
| nonn
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com), Jan 07 2001
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