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 A022500 #14 Jan 05 2018 22:01:47
%S A022500 4,41,4111,4113,411231,4112213111,411222113113,41122312311231,
%T A022500 4112223111213112213111,41122331132111311222113113,
%U A022500 411222321231211331122312311231
%N A022500 Describe the previous term! (method B - initial term is 4).
%C A022500 Method B = 'digit'-indication followed by 'frequency'.
%H A022500 Seiichi Manyama, <a href="/A022500/b022500.txt">Table of n, a(n) for n = 1..23</a>
%e A022500 E.g. the term after 4113 is obtained by saying "4 once, 1 twice, 3 once", which gives 411231.
%t A022500 a[1] = 4;
%t A022500 a[n_] := a[n] = {#[[1]], Length[#]}& /@ Split[a[n-1] // IntegerDigits] // Flatten // FromDigits;
%t A022500 Array[a, 11] (* _Jean-François Alcover_, Jul 13 2016 *)
%Y A022500 Cf. A007651, A022470, A022499, A022501-A022505.
%K A022500 nonn,base,easy,nice
%O A022500 1,1
%A A022500 _N. J. A. Sloane_