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 A022507 #15 Feb 16 2025 08:32:34
%S A022507 3,13,1311,211311,21132112,122112132112,122112131112212211,
%T A022507 2122112231131112212211,21221122311321132221221112,
%U A022507 12312211321321121321132221221112
%N A022507 Describe previous term from the right (method A - initial term is 3).
%C A022507 Method A = 'frequency' followed by 'digit'-indication.
%H A022507 Reinhard Zumkeller, <a href="/A022507/b022507.txt">Table of n, a(n) for n = 0..21</a>
%H A022507 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/LookandSaySequence.html">Look and Say Sequence</a>
%H A022507 Wikipedia, <a href="http://en.wikipedia.org/wiki/Look-and-say_sequence">Look-and-say sequence</a>
%F A022507 a(n+1) = A045918(A004086(a(n))). - _Reinhard Zumkeller_, Mar 02 2014
%e A022507 The term after 1311 is obtained by saying "two 1's, one 3, one 1", which gives 211311.
%t A022507 A022507[1]:=3;A022507[n_]:=A022507[n]=FromDigits[Flatten[{Length[#],First[#]}&/@Split[Reverse[IntegerDigits[A022507[n-1]]]]]];Map[A022507,Range[15]] (* _Peter J. C. Moses_, Apr 22 2013 *)
%o A022507 (Haskell)
%o A022507 a022507 n = a022507_list !! n
%o A022507 a022507_list = iterate (a045918 . a004086) 3
%o A022507 -- _Reinhard Zumkeller_, Mar 02 2014
%Y A022507 Cf. A022506, A006711, A022482, A022508-A022513.
%K A022507 nonn,base,easy,nice
%O A022507 0,1
%A A022507 _N. J. A. Sloane_
%E A022507 More terms from _Erich Friedman_