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 A293289 #23 Nov 16 2017 02:51:28
%S A293289 1,8,28,76,204,580,1556,4180,11204,29724,79276,212076,565692,1509332,
%T A293289 4026028,10740796,28646804,76396620,203728972,543283204,1448779164,
%U A293289 3863345612,10302538780,27473690092,73263231116,195369181668,520985280228,1389296277316,3704793953044
%N A293289 Number of level n squares on a Sierpinski carpet that intersect the edge of a circle with the same center and diameter.
%C A293289 There are 8^n level n squares on a Sierpinski carpet.
%C A293289 The terms of this sequence have a common factor 4 except a(0).
%C A293289 Lim_{n->infinity} a(n)/a(n-1) = 8/3.
%C A293289 Lim_{n->infinity} a(n)/(8/3)^n = 4.38167....
%H A293289 Yi Yang, <a href="/A293289/b293289.txt">Table of n, a(n) for n = 0..32</a>
%H A293289 Chyanog, <a href="/A293289/a293289.png">Illustration of initial terms</a> (the blue squares are counted)
%H A293289 Wayne, Ickiverar, <a href="http://bbs.emath.ac.cn/thread-9655-4-1.html">The C++ code generating the sequence</a>
%Y A293289 Cf. A094976, A242118, A293288.
%K A293289 nonn
%O A293289 0,2
%A A293289 _Yi Yang_, Oct 05 2017