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Number of values of k for which phi(k) is a permutation of decimal digits of k, for 10^(n-1) < k < 10^n.
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%I #26 May 19 2024 02:10:29

%S 1,2,2,16,57,325,1666,9787,58979,366329

%N Number of values of k for which phi(k) is a permutation of decimal digits of k, for 10^(n-1) < k < 10^n.

%F a(n) = # { k in A115921 | 10^(n-1) < k < 10^n }. - _M. F. Hasler_, Feb 24 2014

%e a(3) = 2 because the values of k satisfying the condition for 10^2 < k < 10^3 are {291, 502}. - _V. Raman_, Feb 17 2014

%o (PARI) a(n)=sum(k=10^(n-1), 10^n, vecsort(digits(k)) == vecsort(digits(eulerphi(k)))) \\ _V. Raman_, Feb 17 2014, based on edits by _M. F. Hasler_

%Y Cf. A000010 (phi), A115921.

%K nonn,base,more

%O 1,2

%A _V. Raman_, Sep 06 2012

%E a(9)-a(10) from _Amiram Eldar_, May 19 2024