OFFSET
1,1
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..1000
EXAMPLE
n=15: cototient(15) = 7, sigma_3(15) = 3528 = 72 * 49.
MATHEMATICA
Do[s=DivisorSigma[3, n]/(n-EulerPhi[n])^2; If[IntegerQ[s]&&!PrimeQ[n], Print[n]], {n, 1, 100000}]
PROG
(PARI) isok(n) = (n!=1) && !isprime(n) && !(sigma(n, 3)%(n-eulerphi(n))^2); \\ Michel Marcus, Aug 13 2019
CROSSREFS
KEYWORD
nonn
AUTHOR
Labos Elemer, Feb 03 2004
STATUS
approved