OFFSET
1,2
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..1000
FORMULA
Conjecture : Limit_{n -> infinity} log(a(n))/log(n) exists and = 2.6... .
MATHEMATICA
Select[Range[20000], Divisible[DivisorSigma[1, #+1]-DivisorSigma[1, #], EulerPhi[#]]&] (* Harvey P. Dale, Sep 15 2011 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Benoit Cloitre, Aug 07 2002
STATUS
approved