A058817 Even cototient numbers.

0, 2, 4, 6, 8, 12, 14, 16, 18, 20, 22, 24, 28, 30, 32, 36, 38, 40, 42, 44, 46, 48, 54, 56, 60, 62, 64, 66, 68, 70, 72, 74, 76, 78, 80, 82, 84, 88, 90, 92, 94, 96, 98, 102, 104, 106, 108, 110, 112, 114, 118, 120, 124, 126, 128, 132, 136, 138, 140, 142, 144, 148, 150, 152

Offset: 1

Author

Labos Elemer, Jan 04 2001

Keywords

• nonn

Examples

			88 is here because it is the cototient of 120: 88 = 120-phi(120) = 120-32 = 88.
		

Links

• Donovan Johnson, Table of n, a(n) for n = 1..10001

Crossrefs

Cf. A000010, A051953, A063742, A005277, A005278, A002202, A058763.

Programs

Mathematica

With[{max = 300}, Union@ Select[Table[n - EulerPhi[n], {n, 1, max^2}], # < max && EvenQ[#] &]] (* Amiram Eldar, Jan 12 2024 *)

Formula

Even terms of A063742.

Extensions

Offset corrected by Donovan Johnson, Nov 17 2013

a(1) = 0 inserted by Amiram Eldar, Jan 12 2024