OFFSET
1,1
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
EXAMPLE
81 + sigma(81) + phi(81) = 16^2.
MATHEMATICA
Select[Range[30000], IntegerQ@Sqrt[# +DivisorSigma[1, #]+EulerPhi[#]] &] (* Amiram Eldar, Aug 13 2019 *)
PROG
(PARI) isok(n) = issquare (n + sigma(n) + eulerphi(n)); \\ Michel Marcus, Jan 26 2014
CROSSREFS
KEYWORD
nonn
AUTHOR
Giovanni Resta, Feb 13 2006
STATUS
approved