OFFSET
1,2
LINKS
Hiroaki Yamanouchi, Table of n, a(n) for n = 1..387
MATHEMATICA
lst={}; Do[u = EulerPhi@n; If[u == DivisorSigma[1, EulerPhi@u], AppendTo[lst, n]], {n, 10^6}]; lst
PROG
(PARI)
for(n=1, 10^7, if(eulerphi(n)==sigma(eulerphi(eulerphi(n))), print1(n, ", "))) \\ Derek Orr, Sep 19 2014
(Magma) [n: n in [1..2*10^6] | EulerPhi(n) eq DivisorSigma(1, EulerPhi(EulerPhi(n)))]; // Vincenzo Librandi, Dec 25 2015
CROSSREFS
KEYWORD
nonn
AUTHOR
Giovanni Resta, Jan 22 2006
EXTENSIONS
a(35)-a(36) from Hiroaki Yamanouchi, Sep 19 2014
STATUS
approved