A116002 n*phi(n)*phi(phi(n)) is a square.

1, 8, 27, 32, 108, 128, 243, 250, 432, 512, 686, 972, 1000, 1331, 1728, 2048, 2187, 2197, 2744, 3375, 3888, 4000, 5324, 6174, 6250, 6912, 8192, 8748, 8788, 9826, 10976, 13500, 15552, 16000, 19683, 19773, 21296, 24696, 25000, 27648, 30375

Offset: 1

Author

Giovanni Resta, Feb 13 2006

Keywords

• nonn

Examples

			15552*phi(15552)*phi(phi(15552))=373248^2.
		

Links

• Harvey P. Dale, Table of n, a(n) for n = 1..220

Crossrefs

Cf. A055744.

Programs

Mathematica

esQ[n_]:=Module[{e=EulerPhi[n]},IntegerQ[Sqrt[n e EulerPhi[e]]]]; Select[Range[31000],esQ] (* Harvey P. Dale, Dec 16 2011 *)