A116042 n+phi(n)+phi(phi(n)) is a cube.

15, 40, 293, 320, 723, 967, 1057, 1173, 2560, 4104, 5287, 6680, 10312, 14537, 16472, 18040, 18785, 19288, 19521, 20480, 22297, 27129, 32832, 32902, 33929, 36563, 38507, 53352, 53440, 80200, 82496, 85995, 86429, 98227, 101593, 105273, 106712, 110808, 111321

Offset

1,1

Links

Hiroaki Yamanouchi, Table of n, a(n) for n = 1..1224

Example

80200+phi(80200)+phi(phi(80200)) = 125000 = 50^3.

Mathematica

nepQ[n_]:=Module[{epn=EulerPhi[n]}, IntegerQ[Power[n+epn+ EulerPhi[epn], (3)^-1]]]; Select[Range[110000], nepQ]  (* Harvey P. Dale, Apr 11 2011 *)

Prog

(PARI)
for(n=1, 10^7, p = n+eulerphi(n)+eulerphi(eulerphi(n)); if(ispower(p)&&ispower(p)%3==0, print1(n, ", "))) \\ Derek Orr, Sep 19 2014

Crossrefs

Cf. A116040, A116041, A116043.

Sequence in context: A038991 A068020 A131991 * A219378 A280045 A103003

Adjacent sequences: A116039 A116040 A116041 * A116043 A116044 A116045

Keyword

nonn

Author

Giovanni Resta, Feb 13 2006

Extensions

a(37)-a(39) from Hiroaki Yamanouchi, Sep 19 2014

Status

approved