A115921 Numbers k such that the decimal digits of phi(k) are a permutation of those of k.

1, 21, 63, 291, 502, 2518, 2817, 2991, 4435, 5229, 5367, 5637, 6102, 6174, 6543, 6822, 7236, 7422, 8022, 8541, 8982, 17631, 18231, 18261, 20301, 20518, 20617, 21058, 22471, 22851, 25196, 25918, 27615, 29817, 34816, 35683, 43218, 44305

Offset: 1

Author

Giovanni Resta, Feb 06 2006

Keywords

• nonn
• base

Comments

Contains A069215 and A113781; is itself a subsequence of A082060. - M. F. Hasler, Nov 28 2007

There is some m > 1 such that a(n) > m*n for all n > 1. This follows from the positive density of numbers n such that n/phi(n) > 10. - Charles R Greathouse IV, Sep 07 2012

Examples

			phi(20301) = 13200, phi(6543) = 4356.
		

Links

• V. Raman, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A069215, A113781, A082060, A115920, A114065, A175795.

Programs

Mathematica

Select[Range[45000],Sort[IntegerDigits[EulerPhi[#]]]==Sort[IntegerDigits[#]]&] (* Harvey P. Dale, Jul 25 2018 *)

PARI

for(n=1,10^5,if(vecsort(Vecsmall(Str(n)))==vecsort(Vecsmall(Str(eulerphi(n)))),print1(n", "))) \\ M. F. Hasler, Nov 28 2007

Python

from sympy import totient
A115921_list = [n for n in range(1,10**4) if sorted(str(totient(n))) == sorted(str(n))] # Chai Wah Wu, Dec 13 2015

Extensions

Edited by M. F. Hasler, Nov 28 2007