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 A121684 Union of {8, 9, 18}, S, 2S and 4S, where S = odd squarefree numbers (A056911). 3
 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 17, 18, 19, 20, 21, 22, 23, 26, 28, 29, 30, 31, 33, 34, 35, 37, 38, 39, 41, 42, 43, 44, 46, 47, 51, 52, 53, 55, 57, 58, 59, 60, 61, 62, 65, 66, 67, 68, 69, 70, 71, 73, 74, 76, 77, 78, 79, 82, 83, 84, 85, 86, 87, 89, 91, 92, 93, 94, 95, 97 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Numbers n such that the cyclic group Z_n is a CI-group. LINKS B. Alspach and M. Mishna, Enumeration of Cayley graphs and digraphs, Discr. Math., 256 (2002), 527-539. M. Mishna, Home Page M. Muzychuk, On Adam's conjecture for circulant graphs, Discr. Math. 167 (1997), 497-510. MATHEMATICA With[{upto=100}, Select[Sort[Join[{8, 9, 18}, Flatten[{#, 2#, 4#}&/@ Select[ Range[1, upto, 2], SquareFreeQ]]]], #<=upto&]] (* Harvey P. Dale, Sep 03 2015 *) CROSSREFS Cf. A121176, A078779. Sequence in context: A253781 A037144 A337379 * A191853 A123093 A191932 Adjacent sequences:  A121681 A121682 A121683 * A121685 A121686 A121687 KEYWORD nonn AUTHOR N. J. A. Sloane, Sep 13 2006 STATUS approved

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Last modified September 20 01:16 EDT 2020. Contains 337234 sequences. (Running on oeis4.)