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 A285395 #12 Sep 08 2022 08:46:19
%S A285395 1,15,249,4371,78693,1431735,26159649,478778379,8768545197,
%T A285395 160633207887,2942987702217,53921188767939,987955842925365,
%U A285395 18101659807680423,331665550405417905,6076909441961837115,111343619823563404797,2040083652208572498111,37379255055440801236953
%N A285395 Start with a single cell at coordinates (0, 0, 0), then iteratively subdivide the grid into 3 X 3 X 3 cells and remove the cells whose sum of modulo 2 coordinates is 1; a(n) is the number of cells after n iterations.
%C A285395 Cell configuration converges to a fractal with dimension 2.647...
%H A285395 G. C. Greubel, <a href="/A285395/b285395.txt">Table of n, a(n) for n = 0..750</a>
%H A285395 Peter Karpov, <a href="http://inversed.ru/InvMem.htm#InvMem_26">InvMem, Item 26</a>
%H A285395 Peter Karpov, <a href="/A285395/a285395.jpg">Illustration of initial terms (n = 1..4)</a>
%H A285395 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (28,-195,324).
%F A285395 a(0) = 1, a(1) = 15, a(2) = 249, a(n) = 28*a(n-1) - 195*a(n-2) + 324*a(n-3).
%F A285395 G.f.: (1-13*x+24*x^2)/(1-28*x+195*x^2-324*x^3).
%t A285395 LinearRecurrence[{28, -195, 324}, {1, 15, 249}, 20]
%o A285395 (Magma) I:=[1,15,249]; [n le 3 select I[n] else 28*Self(n-1) - 195*Self(n-2) + 324*Self(n-3) : n in [1..41]]; // _G. C. Greubel_, Dec 10 2021
%o A285395 (Sage)
%o A285395 def A285395_list(prec):
%o A285395 P.<x> = PowerSeriesRing(ZZ, prec)
%o A285395 return P( (1-13*x+24*x^2)/(1-28*x+195*x^2-324*x^3) ).list()
%o A285395 A285395_list(40) # _G. C. Greubel_, Dec 10 2021
%Y A285395 Cf. A285391, A285392, A285393, A285394, A285396, A285397, A285398, A285399, A285400.
%K A285395 nonn,easy
%O A285395 0,2
%A A285395 _Peter Karpov_, Apr 19 2017