A066663 Numbers n such that phi(n) is a proper substring of n.

1320, 1640, 1768, 1996, 2640, 3960, 13200, 16400, 19984, 19996, 26400, 39600, 132000, 164000, 199996, 264000, 396000, 1320000, 1640000, 1999936, 2640000, 3960000, 13200000, 16400000, 16666240, 17999488, 18515584, 19999984, 19999996

Offset: 1

Author

Vladeta Jovovic, Jan 11 2002

Keywords

• nonn
• base

Comments

Since the ratio n/phi(n) grows very slowly with n (see A091439), this sequence will be equal to A067206 (apart the initial 1) at least for all the terms smaller than 10^103. - Giovanni Resta, Apr 14 2017

Examples

			phi(1320)=320, phi(1640)=640, phi(1768)=768, phi(1996)=996, phi(2640)=640,..., phi(199999999984)=99999999984.
		

Links

• Giovanni Resta, Table of n, a(n) for n = 1..65 (terms < 10^12)

Crossrefs

Cf. A000010, A036433, A091439, A067206.

Programs

Mathematica

Select[Range[2, 10^5], StringPosition[ ToString@ #, ToString@ EulerPhi@ #] != {} &] (* Giovanni Resta, Apr 14 2017 *)

Extensions

Offset corrected and a(19)-a(29) from Donovan Johnson, May 08 2010