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A198802 Closed paths whose steps are roots of unity. Un(18) 0
1, 0, 18, 36, 918, 5400, 82800, 801360, 10907190, 132053040, 1802041668, 24199809480, 340640607384, 4834708246368, 70229958125184, 1032223723667136, 15391538570569590, 231935110984687968, 3531542904056225916, 54244559313713885688, 839979883121036697468 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

COMMENTS

Un(18), comment in article) : For each n >= 1, the sequence (Un(N))N >= 0 is P-recursive but is not algebraic when n > 2.

REFERENCES

Gilbert Labelle and Annie Lacasse, Closed paths whose steps are roots of unity, in FPSAC 2011, Reykjav┬┤k, Iceland DMTCS proc. AO, 2011, 599-610;

LINKS

Table of n, a(n) for n=0..20.

CROSSREFS

Sequence in context: A204824 A115550 A061713 * A041638 A041636 A212428

Adjacent sequences:  A198799 A198800 A198801 * A198803 A198804 A198805

KEYWORD

nonn

AUTHOR

Simon Plouffe, Oct 30 2011

STATUS

approved

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Last modified July 29 08:51 EDT 2014. Contains 245020 sequences.