A114072 Numbers k such that phi(k) + k is a fourth power.

12, 41, 172, 176, 192, 313, 385, 972, 1008, 1201, 2732, 2752, 2816, 3072, 6668, 7321, 14281, 15552, 16128, 25616, 29425, 41761, 43696, 43712, 44032, 45056, 49152, 78732, 78768, 79056, 81648, 84240, 97241, 106688, 123921, 139921

Offset: 1

Author

Giovanni Resta, Feb 13 2006

Keywords

• nonn

Examples

			phi(41) + 41 = 81 = 3^4.
		

Links

• Amiram Eldar, Table of n, a(n) for n = 1..500

Crossrefs

Cf. A000010, A121048, subsequence of A114073.

Programs

Mathematica

Select[Range[140000],IntegerQ[Surd[#+EulerPhi[#],4]]&] (* Harvey P. Dale, Sep 27 2020 *)

PARI

isok(n) = ispower(eulerphi(n) + n, 4); \\ Michel Marcus, Jan 09 2014