OFFSET
1,1
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
EXAMPLE
For n=12: sigma(12)=28, phi(12)=4, gcd(28,4)=4 core(12)=6, sigma(6)=12, phi(6)=2, gcd(12,2)=2.
MATHEMATICA
ffi[x_] := Flatten[FactorInteger[x]] lf[x_] := Length[FactorInteger[x]] ba[x_] := Table[Part[ffi[x], 2*w-1], {w, 1, lf[x]}] cor[x_] := Apply[Times, ba[x]] g1[x_] := GCD[DivisorSigma[1, x], EulerPhi[x]] g2[x_] := GCD[DivisorSigma[1, cor[x]], EulerPhi[cor[x]]] Do[s1=g1[n]; s2=g2[n]; If[Greater[s1, s2], Print[n]], {n, 1, 256}]
CROSSREFS
KEYWORD
nonn
AUTHOR
Labos Elemer, Oct 17 2002
STATUS
approved