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 A007890 #22 Aug 20 2020 01:18:18
%S A007890 1,11,21,1211,1231,131221,132231,232221,134211,14131231,14231241,
%T A007890 24132231,14233221,14233221,14233221,14233221,14233221,14233221,
%U A007890 14233221,14233221,14233221,14233221,14233221,14233221,14233221,14233221,14233221,14233221
%N A007890 Summarize the previous term! (in decreasing order).
%H A007890 Onno M. Cain, Sela T. Enin, <a href="https://arxiv.org/abs/2004.00209">Inventory Loops (i.e. Counting Sequences) have Pre-period 2 max S_1 + 60</a>, arXiv:2004.00209 [math.NT], 2020.
%F A007890 From _Seiichi Manyama_, Aug 18 2020: (Start)
%F A007890 a(1) = 1 and a(n) = A244112(a(n-1)) for n > 1.
%F A007890 a(n) = 14233221 for n >= 13. (End)
%e A007890 For example, the term after 131221 is obtained by saying "one 3, two 2's, three 1's", which gives 13-22-31, i.e. 132231.
%t A007890 Nest[Append[#, FromDigits@ Flatten@ Map[Reverse, Tally@ ReverseSort@ IntegerDigits@ #[[-1]] ] ] &, {1}, 24] (* _Michael De Vlieger_, Jul 15 2020 *)
%Y A007890 Cf. A005150, A034003, A036058, A244112.
%K A007890 nonn,base,easy
%O A007890 1,2
%A A007890 _Mira Bernstein_