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 A255471 #12 Feb 05 2017 04:41:51 %S A255471 1,6,24,100,396,1596,6364,25500,101916,407836,1631004,6524700, %T A255471 26097436,104392476,417564444,1670268700,6681052956,26724255516, %U A255471 106896934684,427587913500,1710351304476,6841405916956,27365622269724,109462491875100,437849961907996,1751399858816796,7005599412897564,28022397696329500,112089590695839516 %N A255471 a(n) = A255470(2^n-1). %H A255471 Colin Barker, <a href="/A255471/b255471.txt">Table of n, a(n) for n = 0..1000</a> %H A255471 Shalosh B. Ekhad, N. J. A. Sloane, and Doron Zeilberger, <a href="http://arxiv.org/abs/1503.01796">A Meta-Algorithm for Creating Fast Algorithms for Counting ON Cells in Odd-Rule Cellular Automata</a>, arXiv:1503.01796 [math.CO], 2015; see also the <a href="http://www.math.rutgers.edu/~zeilberg/mamarim/mamarimhtml/CAcount.html">Accompanying Maple Package</a>. %H A255471 Shalosh B. Ekhad, N. J. A. Sloane, and Doron Zeilberger, <a href="http://arxiv.org/abs/1503.04249">Odd-Rule Cellular Automata on the Square Grid</a>, arXiv:1503.04249 [math.CO], 2015. %H A255471 N. J. A. Sloane, On the No. of ON Cells in Cellular Automata, Video of talk in Doron Zeilberger's Experimental Math Seminar at Rutgers University, Feb. 05 2015: <a href="https://vimeo.com/119073818">Part 1</a>, <a href="https://vimeo.com/119073819">Part 2</a> %H A255471 N. J. A. Sloane, <a href="http://arxiv.org/abs/1503.01168">On the Number of ON Cells in Cellular Automata</a>, arXiv:1503.01168 [math.CO], 2015. %H A255471 <a href="/index/Ce#cell">Index entries for sequences related to cellular automata</a> %H A255471 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (3,6,-8). %F A255471 G.f.: (1+3*x)/((1-x)*(1+2*x)*(1-4*x)). %F A255471 From _Colin Barker_, Feb 04 2017: (Start) %F A255471 a(n) = (-4 - (-2)^n + 7*2^(1+2*n)) / 9. %F A255471 a(n) = 3*a(n-1) + 6*a(n-2) - 8*a(n-3) for n>2. %F A255471 (End) %o A255471 (PARI) Vec((1+3*x) / ((1-x)*(1+2*x)*(1-4*x)) + O(x^30)) \\ _Colin Barker_, Feb 04 2017 %Y A255471 Cf. A255470. %K A255471 nonn,easy %O A255471 0,2 %A A255471 _N. J. A. Sloane_ and _Doron Zeilberger_, Feb 23 2015