OFFSET
1,1
LINKS
Michael De Vlieger, Table of n, a(n) for n = 1..10000
EXAMPLE
m = 45 - 3*3*5 and sigma(45) = 78 < 2m = 90.
MATHEMATICA
Select[Range@ 280, And[! SquareFreeQ@ #, DivisorSigma[1, #] < 2 #] &] (* Michael De Vlieger, Mar 25 2017 *)
PROG
(PARI) isok(n) = !issquarefree(n) && (sigma(n) < 2*n); \\ Michel Marcus, Dec 18 2013
(Python)
from sympy import divisor_sigma
from sympy.ntheory.factor_ import core
print([n for n in range(1, 301) if core(n) != n and divisor_sigma(n)<2*n]) # Indranil Ghosh, Mar 26 2017
CROSSREFS
KEYWORD
nonn
AUTHOR
Labos Elemer, Sep 05 2003
STATUS
approved