OFFSET
1,1
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
FORMULA
n such that A057021(n)=4.
MATHEMATICA
Select[Range[500], Denominator[DivisorSigma[1, #]/DivisorSigma[0, #]] == 4 &] (* Amiram Eldar, Sep 08 2019 *)
PROG
(Magma) [n:n in [1..2100]|Denominator(SumOfDivisors(n)/#Divisors(n)) eq 4]; // Marius A. Burtea, Sep 08 2019
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Benoit Cloitre, Apr 05 2002
STATUS
approved