A078779 Union of S, 2S and 4S, where S = odd squarefree numbers (A056911).

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

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 * A351958 A047593 A181046

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