OFFSET
1,1
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..108
EXAMPLE
81 + sigma(81) + phi(81) = 4^4.
MATHEMATICA
Select[Range[2*10^6], IntegerQ[Surd[# + DivisorSigma[1, #] + EulerPhi[#], 4]] &] (* Amiram Eldar, Dec 15 2023 *)
PROG
(PARI) isok(n) = ispower(n + sigma(n) + eulerphi(n), 4); \\ Michel Marcus, Jan 25 2014
CROSSREFS
KEYWORD
nonn
AUTHOR
Giovanni Resta, Feb 13 2006
EXTENSIONS
a(15)-a(25) from Donovan Johnson, Jul 02 2010
a(26)-a(29) from Amiram Eldar, Dec 15 2023
STATUS
approved