OFFSET
1,2
COMMENTS
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..1000
EXAMPLE
170 is in the sequence since phi(170) = 64 = 8^2, sigma(170) = psi(170) = 324 = 18^2.
25264008, the first nonsquarefree term ( > 1 ) in the sequence, has phi = 2520^2, sigma = 9600^2 and psi = 8064^2.
MATHEMATICA
a = {}; psi[n_] := DirichletConvolve[j, MoebiusMu[j]^2, j, n];
aQ[n_] := AllTrue[Sqrt[{DivisorSigma[1, n], EulerPhi[n], psi[n]}], IntegerQ];
Do[If[aQ[k], AppendTo[a, k]], {k, 1, 10^7}]; a
CROSSREFS
KEYWORD
nonn
AUTHOR
Amiram Eldar, Mar 28 2018
STATUS
approved