OFFSET
1,2
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
EXAMPLE
All primes are here.
Numerous composite solutions:See A087247.
n=21=3.7 and sigma[21]=1+3+7+21=32<2.21=42.
MATHEMATICA
Select[Range[120], SquareFreeQ[#] && DivisorSigma[1, #] < 2 # &] (* Amiram Eldar, Aug 03 2019 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Labos Elemer, Sep 09 2003
STATUS
approved