OFFSET
1,1
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..8225
MATHEMATICA
Select[Range[5000], DivisorSigma[1, #+1] == 4*EulerPhi[#] &] (* Amiram Eldar, Apr 24 2022 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Benoit Cloitre, Feb 21 2002
STATUS
approved