OFFSET
1,1
COMMENTS
Complement of A014567(n).
Also, numbers n such that the reduced denominator of Sum_{d|n} 1/d (A017666) is less than n. - Ivan Neretin, Aug 30 2015
The asymptotic density of this sequence is 1 (Dressler, 1974; Luca, 2007). - Amiram Eldar, May 23 2022
LINKS
Reinhard Zumkeller, Table of n, a(n) for n = 1..10000
Robert E. Dressler, On a theorem of Niven, Canadian Mathematical Bulletin, Vol. 17, No. 1 (1974), pp. 109-110.
Florian Luca, On the densities of some subsets of integers, Missouri Journal of Mathematical Sciences, Vol. 19, No. 3 (2007), pp. 167-170.
FORMULA
A009194(a(n)) > 1. - Reinhard Zumkeller, Mar 23 2013
MAPLE
select(n -> igcd(n, numtheory:-sigma(n)) > 1, [$1..1000]); # Robert Israel, Sep 01 2015
MATHEMATICA
Select[Range@125, GCD[#, DivisorSigma[1, #]] > 1 &] (* Ivan Neretin, Aug 30 2015 *)
PROG
(PARI) for(n=1, 160, if(gcd(sigma(n), n)>1, print1(n, ", ")))
(Haskell)
a069059 n = a069059_list !! (n-1)
a069059_list = filter ((> 1) . a009194) [1..]
-- Reinhard Zumkeller, Mar 23 2013
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Benoit Cloitre, Apr 04 2002
STATUS
approved