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 A209644 #17 Oct 16 2015 23:01:18 %S A209644 0,1,20,11,300,210,120,111,4000,3100,2200,1300,2110,1210,1120,1111, %T A209644 50000,41000,32000,23000,14000,31100,22100,13100,21200,12200,11300, %U A209644 21110,12110,11210,11120,11111,600000,510000,420000,330000,240000,150000,411000,321000,231000,141000,312000,222000,132000,213000 %N A209644 Łukasiewicz words (without the last zero) for rooted plane trees where non-leaf branching can occur only at the leftmost branch of any level, but nowhere else. %C A209644 Note: this finite decimal representation works only up to the 511th term, as the 512th such word is already (10,0,0,0,0,0,0,0,0,0). %H A209644 Antti Karttunen, <a href="/A209644/b209644.txt">Table of n, a(n) for n = 0..511</a> %H A209644 A. Karttunen, <a href="/A014486/a014486.pdf">Corresponding Lukasiewicz-words (with a trailing zero) illustrated on 1, 2, 3, 4, 6, 7, 8, 9, 14, 16, 17th, etc. row in this illustration.</a> %H A209644 OEIS Wiki, <a href="/wiki/Łukasiewicz_words">Łukasiewicz words</a> %H A209644 <a href="/index/Lu#Lukasiewicz">Index entries for sequences related to Łukasiewicz</a> %F A209644 a(n) = A071153(A209643(n)). %Y A209644 A209643 gives the positions of these terms in A071153 (A014486). %Y A209644 Cf. A071160. %K A209644 nonn,base,fini %O A209644 0,3 %A A209644 _Antti Karttunen_, Mar 24 2012