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 A022499 #17 Jan 05 2018 22:01:39
%S A022499 3,31,3111,3113,311231,3112213111,311222113113,31122312311231,
%T A022499 3112223111213112213111,31122331132111311222113113,
%U A022499 311222321231211331122312311231
%N A022499 Describe the previous term! (method B - initial term is 3).
%C A022499 Method B = 'digit'-indication followed by 'frequency'.
%H A022499 Seiichi Manyama, <a href="/A022499/b022499.txt">Table of n, a(n) for n = 1..23</a>
%e A022499 E.g. the term after 3113 is obtained by saying "3 once, 1 twice, 3 once", which gives 311231.
%t A022499 a[1] = 3;
%t A022499 a[n_] := a[n] = {#[[1]], Length[#]}& /@ Split[a[n-1] // IntegerDigits] // Flatten // FromDigits;
%t A022499 Array[a, 11] (* _Jean-François Alcover_, Jul 13 2016, updated Jan 05 2018 *)
%Y A022499 Cf. A007651, A022470, A022500-A022505.
%Y A022499 Cf. A006715.
%K A022499 nonn,base,easy,nice
%O A022499 1,1
%A A022499 _N. J. A. Sloane_