

A161787


Number of (undirected) cycles in the graph with nodes labeled 1..n, and nodes i and j joined by an edge if i divides j or vice versa.


1



0, 0, 0, 1, 1, 6, 6, 18, 25, 42, 42, 241, 241, 324, 667, 1602, 1602, 5511, 5511, 21596, 32549, 35434, 35434, 237727, 270992, 292057, 421656, 1140425, 1140425, 7609789, 7609789, 19163336, 22436043, 23293234, 46391754, 313698907, 313698907, 324745136, 370720970, 2113744875
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OFFSET

1,6


COMMENTS

Old definition was "Number of unique loops in a map of 1 to N vertices, with nondirectional connections between vertices which are factors or multiples of each other".


LINKS



EXAMPLE

Case n=4: The only cycle is 124.
Case n=6: The 6 cycles are 124, 126, 136, 1362, 13624, 1624.
(End)


CROSSREFS



KEYWORD

nonn,obsc


AUTHOR

David Eaton (dave(AT)suave.net), Jun 19 2009


EXTENSIONS

Name clarified, a(21) corrected and a(25)a(40) from Andrew Howroyd, Aug 26 2017


STATUS

approved



