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A078779 Union of S, 2S and 4S, where S = odd squarefree numbers (A056911). 7
1, 2, 3, 4, 5, 6, 7, 10, 11, 12, 13, 14, 15, 17, 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, 101 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Numbers n such that the cyclic group Z_n is a DCI-group.

Numbers n such that A008475(n) = A001414(n).

A193551(a(n)) = A000026(a(n)) = a(n). - Reinhard Zumkeller, Aug 27 2011

Union of squarefree numbers and twice the squarefree numbers (A005117). - Reinhard Zumkeller, Feb 11 2012

The complement is A046790. - Omar E. Pol, Jun 11 2016

LINKS

T. D. Noe, Table of n, a(n) for n = 1..7098

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.

FORMULA

a(n) = (Pi^2/7)*n + O(sqrt(n)). - Vladimir Shevelev, Jun 08 2016

PROG

(Haskell)

a078779 n = a078779_list !! (n-1)

a078779_list = m a005117_list $ map (* 2) a005117_list where

   m xs'@(x:xs) ys'@(y:ys) | x < y     = x : m xs ys'

                           | x == y    = x : m xs ys

                           | otherwise = y : m xs' ys

-- Reinhard Zumkeller, Feb 11 2012, Aug 27 2011

(PARI) is(n)=issquarefree(n/gcd(n, 2)) \\ Charles R Greathouse IV, Nov 05 2017

CROSSREFS

Cf. A121176, A121684, A008475, A001414, A046790.

Sequence in context: A035060 A231272 A143719 * A047593 A181046 A032879

Adjacent sequences:  A078776 A078777 A078778 * A078780 A078781 A078782

KEYWORD

nonn

AUTHOR

Benoit Cloitre, Jan 11 2003

EXTENSIONS

Edited by N. J. A. Sloane, Sep 13 2006

STATUS

approved

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Last modified January 23 07:07 EST 2020. Contains 331168 sequences. (Running on oeis4.)