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 A037220 #17 Feb 17 2024 10:30:18 %S A037220 0,10,1011,1031,102113,10311213,10411223,1031221314,1041222314, %T A037220 1031321324,1031223314,1031223314,1031223314,1031223314,1031223314, %U A037220 1031223314,1031223314,1031223314,1031223314,1031223314,1031223314 %N A037220 Summarize the previous term!. %e A037220 a(0) is given as 0; %e A037220 a(1) is one zero -> 10; %e A037220 a(2) is one zero and one one -> 1011; %e A037220 a(3) is one zero and three ones -> 1031; %e A037220 a(7) and onward is 1031223314. %t A037220 NestList[ FromDigits@ Flatten@ Map[IntegerDigits@ Reverse@# &, Sort@ Tally@ Flatten@ IntegerDigits@#] &, 0, 20] (* _Robert G. Wilson v_, Nov 28 2019, adapted from code by _Michael De Vlieger_ in A177359 *) %Y A037220 Cf. A005151. %K A037220 nonn,base,easy %O A037220 0,2 %A A037220 _N. J. A. Sloane_