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 A077896 #17 Feb 16 2025 08:32:48
%S A077896 1,0,3,0,7,0,15,0,31,0,63,0,127,0,255,0,511,0,1023,0,2047,0,4095,0,
%T A077896 8191,0,16383,0,32767,0,65535,0,131071,0,262143,0,524287,0,1048575,0,
%U A077896 2097151,0,4194303,0,8388607,0,16777215,0,33554431,0,67108863,0,134217727,0,268435455
%N A077896 Expansion of (1-x)^(-1)/(1+x-2*x^2-2*x^3).
%C A077896 Also, the decimal representation of the diagonal from the corner to the origin of the n-th stage of growth of the two-dimensional cellular automaton defined by "Rule 276", based on the 5-celled von Neumann neighborhood, initialized with a single black (ON) cell at stage zero. - _Robert Price_, May 25 2017
%D A077896 S. Wolfram, A New Kind of Science, Wolfram Media, 2002; p. 170.
%H A077896 Vincenzo Librandi, <a href="/A077896/b077896.txt">Table of n, a(n) for n = 0..1000</a>
%H A077896 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 A077896 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/ElementaryCellularAutomaton.html">Elementary Cellular Automaton</a>
%H A077896 S. Wolfram, <a href="http://wolframscience.com/">A New Kind of Science</a>
%H A077896 Wolfram Research, <a href="http://atlas.wolfram.com/">Wolfram Atlas of Simple Programs</a>
%H A077896 <a href="/index/Ce#cell">Index entries for sequences related to cellular automata</a>
%H A077896 <a href="https://oeis.org/wiki/Index_to_2D_5-Neighbor_Cellular_Automata">Index to 2D 5-Neighbor Cellular Automata</a>
%H A077896 <a href="https://oeis.org/wiki/Index_to_Elementary_Cellular_Automata">Index to Elementary Cellular Automata</a>
%H A077896 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (0,3,0,-2).
%F A077896 G.f.: 1/((1 - x)*(1 + x)*(1 - 2*x^2)). - _Bruno Berselli_, May 26 2017
%F A077896 a(n) = (1 + (-1)^n)*(2^floor((n + 3)/2) - 1)/2. - _Vincenzo Librandi_, May 27 2017
%t A077896 CoefficientList[Series[(1 - x)^(-1) / (1 + x - 2 x^2 - 2 x^3), {x, 0, 60}], x] (* _Vincenzo Librandi_, May 26 2017 *)
%o A077896 (Magma) [(1+(-1)^n)*(2^Floor((n+3)/2)-1)/2: n in [0..60]]; // _Vincenzo Librandi_, May 26 2017
%Y A077896 Cf. A287468, A287469, A287470.
%K A077896 nonn,easy
%O A077896 0,3
%A A077896 _N. J. A. Sloane_, Nov 17 2002