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

Author

Benoit Cloitre, Jan 11 2003

Keywords

• nonn

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.

Crossrefs

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

Programs

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

Formula

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

Extensions

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