OFFSET
1,2
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 1..1000
MATHEMATICA
Select[Range[20000], GCD[#, EulerPhi[#]] == GCD[EulerPhi[#], DivisorSigma[1, #]] == GCD[#, DivisorSigma[1, #]] == DivisorSigma[0, #] &] (* Jean-François Alcover, Mar 18 2013 *)
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Jayanta Basu, Mar 17 2013
STATUS
approved