OFFSET
1,1
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000 (calculated using data from Jud McCranie, terms 1..1000 from Donovan Johnson)
MATHEMATICA
f[x_] := DivisorSigma[1, x]/EulerPhi[x] Do[s=f[n]; s1=f[2*n]; s2=f[4*n]; If[IntegerQ[s]&&IntegerQ[s1]&&IntegerQ[s2], Print[n]], {n, 1, 1000000}]
CROSSREFS
KEYWORD
nonn
AUTHOR
Labos Elemer, Oct 15 2002
STATUS
approved