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

1,1

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

Links

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

Example

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

Mathematica

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

Crossrefs

Cf. A000010, A036433, A091439, A067206.

Sequence in context: A200202 A255799 A023318 * A067206 A248857 A260839

Adjacent sequences: A066660 A066661 A066662 * A066664 A066665 A066666

Keyword

nonn,base

Author

Vladeta Jovovic, Jan 11 2002

Extensions

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

Status

approved