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 A269178 #5 Feb 23 2016 12:09:25 %S A269178 0,3,6,7,11,12,14,15,19,22,24,27,28,30,35,38,44,47,48,51,54,55,56,60, %T A269178 67,70,76,79,88,91,94,95,96,99,102,103,107,108,110,111,112,119,120, %U A269178 131,134,140,143,152,155,158,159,176,179,182,183,187,188,190,191,192,195,198,199,203,204,206,207,211,214,216,219 %N A269178 Numbers that have a unique finite predecessor in Wolfram's Rule 124 cellular automaton; numbers n for which A269175(n) = 1. %C A269178 The indexing starts from zero, because a(0) = 0 is a special case in this sequence. (Zero is the only number which is its own predecessor). %H A269178 Antti Karttunen, <a href="/A269178/b269178.txt">Table of n, a(n) for n = 0..5141</a> %o A269178 (Scheme, with _Antti Karttunen_'s IntSeq-library) %o A269178 (define A269178 (ZERO-POS 0 0 (COMPOSE -1+ A269175))) %Y A269178 Cf. A269174, A269175. %Y A269178 Subsequence of A269177. %K A269178 nonn %O A269178 0,2 %A A269178 _Antti Karttunen_, Feb 22 2016