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A115921 Numbers n such that the decimal digits of phi(n) are a permutation of those of n. 14
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

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

There is some k > 1 such that a(n) > kn 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

LINKS

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

EXAMPLE

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

MATHEMATICA

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

PROG

(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

CROSSREFS

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

Sequence in context: A170930 A113622 A069215 * A251808 A072395 A113781

Adjacent sequences:  A115918 A115919 A115920 * A115922 A115923 A115924

KEYWORD

nonn,base

AUTHOR

Giovanni Resta, Feb 06 2006

EXTENSIONS

Edited by M. F. Hasler, Nov 28 2007

STATUS

approved

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Last modified June 19 17:37 EDT 2019. Contains 324222 sequences. (Running on oeis4.)