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 A249668 #22 Jun 13 2015 00:55:17 %S A249668 3,4,7,10,15,20,25,30,38,47,55,63,69,79,91,96,105,112,124,134,139,144, %T A249668 152,157,163,168,176,183,187,195,205,217,223,229,239,247,259,273,285, %U A249668 289,295,303,311,323,334,339,343,351,363,375,383,389,397,405,413,423 %N A249668 Population of the n-th generation of the pattern 101//010 in the Life Without Death cellular automaton. %C A249668 Each generation, a cell turns on if it has exactly three neighbors that are on. Cells never turn off. %C A249668 This pattern grows indefinitely. No other connected 3-celled pattern does so. %H A249668 Eric M. Schmidt, <a href="/A249668/b249668.txt">Table of n, a(n) for n = 0..2500</a> %H A249668 LifeWiki, <a href="http://www.conwaylife.com/wiki/Life_without_death">Life without death</a> %H A249668 <a href="/index/Rec#order_07">Index entries for linear recurrences with constant coefficients</a>, signature (1,0,0,0,0,1,-1). (Initial terms do not obey recurrence; see formula section.) %F A249668 For n >= 2108, a(n+6) = a(n) + 260. - _Eric M. Schmidt_, Nov 04 2014 %F A249668 For n >= 2115, a(n) = a(n-1) + a(n-6) - a(n-7). - _Eric M. Schmidt_, Nov 05 2014 %e A249668 Generation 0: %e A249668 101 %e A249668 010 %e A249668 Generation 1: %e A249668 111 %e A249668 010 %e A249668 Generation 2: %e A249668 010 %e A249668 111 %e A249668 111 %e A249668 Generation 3: %e A249668 111 %e A249668 111 %e A249668 111 %e A249668 010 %e A249668 Generation 4: %e A249668 00100 %e A249668 01110 %e A249668 11111 %e A249668 01110 %e A249668 01110 %Y A249668 Cf. A097981, A151725, A151731. %K A249668 nonn %O A249668 0,1 %A A249668 _Eric M. Schmidt_, Nov 03 2014