login
A087244
Nonsquarefree deficient numbers.
6
4, 8, 9, 16, 25, 27, 32, 44, 45, 49, 50, 52, 63, 64, 68, 75, 76, 81, 92, 98, 99, 116, 117, 121, 124, 125, 128, 135, 136, 147, 148, 152, 153, 164, 169, 171, 172, 175, 184, 188, 189, 207, 212, 225, 232, 236, 242, 243, 244, 245, 248, 250, 256, 261, 268, 275, 279
OFFSET
1,1
LINKS
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
KEYWORD
nonn
AUTHOR
Labos Elemer, Sep 05 2003
STATUS
approved