OFFSET
1,1
LINKS
Harvey P. Dale, Table of n, a(n) for n = 1..1000
EXAMPLE
sigma(100)-phi(100)=177=3*59
MATHEMATICA
Select[Range[600], PrimeOmega[DivisorSigma[1, #]-EulerPhi[#]]==2&] (* Harvey P. Dale, Mar 18 2013 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Giovanni Resta, Feb 13 2006
STATUS
approved