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 A022509 #8 Dec 17 2021 06:01:56 %S A022509 5,15,1511,211511,21152112,122112152112,122112151112212211, %T A022509 2122112231151112212211,21221122311521132221221112, %U A022509 12312211321321121521132221221112 %N A022509 Describe previous term from the right (method A - initial term is 5). %C A022509 Method A = 'frequency' followed by 'digit'-indication. %e A022509 The term after 1511 is obtained by saying "two 1's, one 5, one 1", which gives 211511. %Y A022509 Cf. A022506, A006711, A022482, A022507-A022513. %K A022509 nonn,base,easy,nice %O A022509 0,1 %A A022509 _N. J. A. Sloane_ %E A022509 More terms from _Erich Friedman_