OFFSET
1,2
COMMENTS
Numbers n such that the cyclic group Z_n is a DCI-group.
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
KEYWORD
nonn
AUTHOR
Benoit Cloitre, Jan 11 2003
EXTENSIONS
Edited by N. J. A. Sloane, Sep 13 2006
STATUS
approved