OFFSET
1,2
LINKS
Donovan Johnson, Table of n, a(n) for n = 1..10000
EXAMPLE
210 = 2*3*5*7, sigma(210) = 576, phi(210) = 48, 576/48 = 12.
MATHEMATICA
Do[s=DivisorSigma[1, n]/EulerPhi[n]; If[IntegerQ[s]&&!Equal[MoebiusMu[n], 0], k=k+1; Print[n]], {n, 1, 2100000}]
CROSSREFS
KEYWORD
nonn
AUTHOR
Labos Elemer, Dec 06 2002
STATUS
approved