OFFSET
1,1
COMMENTS
EXAMPLE
a(12) = 15, sigma_2(15)/sigma_1(15)=260/24 = 65/6 (not integer).
MATHEMATICA
Select[Range[100], Mod @@ DivisorSigma[{2, 1}, #] > 0 &] (* Amiram Eldar, Mar 22 2024 *)
PROG
(PARI) is(n) = {my(f = factor(n)); sigma(f, 2) % sigma(f); } \\ Amiram Eldar, Mar 22 2024
CROSSREFS
KEYWORD
nonn
AUTHOR
Jaroslav Krizek, Mar 15 2009
EXTENSIONS
More terms from Amiram Eldar, Mar 22 2024
STATUS
approved