OFFSET
1,2
FORMULA
EXAMPLE
n=76: a=sigma(76)=140, b=phi(76)=36, a+b=176, a-b=104, gcd(a,b) = gcd(140,36) = 4 < gcd(a+b,a-b) = gcd(176,104) = 8.
MATHEMATICA
Do[s=GCD[a=DivisorSigma[1, n], b=EulerPhi[n]]; s1=GCD[a+b, a-b]; If[ !Equal[s, s1], Print[{n, a, b, a+b, a-b, s, s1, s1/s}]], {n, 1, 1000}]
CROSSREFS
KEYWORD
nonn
AUTHOR
Labos Elemer, Nov 12 2002
STATUS
approved