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A115921
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Numbers k such that the decimal digits of phi(k) are a permutation of those of k.
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14
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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
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OFFSET
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1,2
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COMMENTS
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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
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LINKS
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EXAMPLE
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phi(20301) = 13200, phi(6543) = 4356.
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MATHEMATICA
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Select[Range[45000], Sort[IntegerDigits[EulerPhi[#]]]==Sort[IntegerDigits[#]]&] (* Harvey P. Dale, Jul 25 2018 *)
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PROG
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(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
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CROSSREFS
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KEYWORD
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nonn,base
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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