This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A216385 #27 Nov 30 2024 06:26:50
%S A216385 1,3,5,21,78,403,2069,11856,70835,437164
%N A216385 Number of values of k for which phi(k) is a permutation of decimal digits of k, for k < 10^n.
%F A216385 a(n) = # { k in A115921 | k < 10^n }. - _M. F. Hasler_, Feb 24 2014
%e A216385 a(3) = 5 because the values of k satisfying the condition for k < 10^3 are {1, 21, 63, 291, 502}. - _V. Raman_, Feb 17 2014
%o A216385 (PARI) a(n)=sum(k=1, 10^n, vecsort(digits(k)) == vecsort(digits(eulerphi(k)))) \\ Use digits(n)=eval(Vec(Str(n))) in old versions of PARI. - _V. Raman_, Feb 17 2014, based on edits by _M. F. Hasler_
%Y A216385 Cf. A115921, A000010.
%K A216385 nonn,base,more
%O A216385 1,2
%A A216385 _V. Raman_, Sep 06 2012
%E A216385 a(9) from _Jinyuan Wang_, Mar 03 2020
%E A216385 a(10) from _Amiram Eldar_, Nov 30 2024