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%I #11 Aug 26 2017 21:36:34
%S 0,0,0,1,1,6,6,18,25,42,42,241,241,324,667,1602,1602,5511,5511,21596,
%T 32549,35434,35434,237727,270992,292057,421656,1140425,1140425,
%U 7609789,7609789,19163336,22436043,23293234,46391754,313698907,313698907,324745136,370720970,2113744875
%N 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.
%C 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".
%H Andrew Howroyd, <a href="/A161787/b161787.txt">Table of n, a(n) for n = 1..50</a>
%e From _Andrew Howroyd_, Aug 26 2017: (Start)
%e Case n=4: The only cycle is 1-2-4.
%e Case n=6: The 6 cycles are 1-2-4, 1-2-6, 1-3-6, 1-3-6-2, 1-3-6-2-4, 1-6-2-4.
%e (End)
%K nonn,obsc
%O 1,6
%A David Eaton (dave(AT)suave.net), Jun 19 2009
%E Partially edited by _N. J. A. Sloane_, Dec 21 2014
%E Name clarified, a(21) corrected and a(25)-a(40) from _Andrew Howroyd_, Aug 26 2017