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 A216390 #26 Mar 02 2020 09:18:19
%S A216390 1,1,5,10,47,200,842,4698,28831
%N A216390 Number of values of k for which sigma(k) is a permutation of decimal digits of k, for 10^(n-1) < k < 10^n.
%F A216390 a(n) = # { k in A115920 | 10^(n-1) < k < 10^n }. - _M. F. Hasler_, Feb 24 2014
%e A216390 a(3) = 5 because the values of k satisfying the condition for 10^2 < k < 10^3 are {258, 270, 276, 609, 639}. - _V. Raman_, Feb 18 2014
%o A216390 (PARI) a(n)=sum(k=10^(n-1), 10^n, vecsort(digits(k)) == vecsort(digits(sigma(k)))) \\ _V. Raman_, Feb 18 2014, based on edits by _M. F. Hasler_
%Y A216390 Cf. A115920, A000203.
%K A216390 nonn,base,more
%O A216390 1,3
%A A216390 _V. Raman_, Sep 06 2012
%E A216390 a(9) from _Jinyuan Wang_, Mar 02 2020