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A356831
Size of the automorphism group for the underlying graph of the divisibility graph of size n.
1
1, 2, 2, 2, 4, 2, 4, 4, 4, 2, 4, 2, 6, 4, 2, 4, 12, 12, 48, 48, 48, 12, 48, 24, 24, 12, 12, 12, 48, 48, 240, 480, 240, 96, 96, 96, 480, 288, 192, 192, 960, 960, 5760, 2880, 2880, 1440, 8640, 4320, 4320, 4320, 2880, 2880, 20160, 20160, 10080, 10080, 10080, 2880, 20160, 20160, 161280, 60480, 60480, 120960, 241920, 120960
OFFSET
1,2
COMMENTS
Define a graph H_n with the natural numbers 1,2,...,n as vertices and edges as follows: For any two vertices, v_1, v_2, there is an edge between v_1 and v_2 if there exists a natural number m > 1 such that v_1 = m * v_2. Thus an edge exists between v_1 and v_2 if v_2 divides v_1. a(n) is the size of the automorphism group on the vertices of H_n.
The first few terms (10) are easy to check on paper. For larger values the implementation of BLISS in the R package igraph was used.
PROG
(C) See links.
CROSSREFS
Sequence in context: A366438 A152674 A072056 * A066012 A063375 A064129
KEYWORD
nonn
AUTHOR
Nils Gaute Voll, Aug 30 2022
STATUS
approved