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A066589
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Let u_n be the group of units mod n (invertible elements in the ring Z_n); a(n) is the number of cyclic subgroups in u_n.
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0
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1, 1, 2, 2, 3, 2, 4, 4, 4, 3, 4, 4, 6, 4, 6, 6, 5, 4, 6, 6, 8, 4, 4, 8, 6, 6, 6, 8, 6, 6, 8, 5, 12, 8
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,3
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PROG
| (GAP) c := CyclicGroup(n); aut := AutomorphismGroup(c); ccl := ConjugacyClasses( aut ); ord := List( ccl, x -> Order( Representative( x ) ) ); num := Sum( List( [ 1 .. Length( ccl ) ], i -> Size( ccl[i] ) / Phi( ord[i] ) ) );
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CROSSREFS
| Sequence in context: A140060 A164341 A124771 * A007897 A180783 A106289
Adjacent sequences: A066586 A066587 A066588 * A066590 A066591 A066592
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KEYWORD
| nonn
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AUTHOR
| Sharon Sela (sharonsela(AT)hotmail.com), Jan 08 2002
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