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 A180603 #14 Jun 21 2022 10:28:03 %S A180603 1,4,8,12,20,20,12,12,20,28,44,48,48 %N A180603 Number of "pieces" of the n-th Brillouin zone of a 2D square lattice. %C A180603 Each Brillouin zone has the same area, and they are all equivalent mod the periodicity of the lattice, but the higher-order ones consist of a set of polygons. This is the number of polygons in that set. %H A180603 Jaroslaw W. Klos, <a href="https://demonstrations.wolfram.com/2DBrillouinZones/">2D Brillouin Zones</a>, Wolfram Demonstrations Project, 2013. %e A180603 The 2nd Brillouin zone consists of 4 right isosceles triangles, so a(2) = 4. The 4th Brillouin zone consists of 8 triangles and 4 kites, so a(4) = 12. %Y A180603 Cf. A180604, A199765, A199766. %K A180603 nonn,more %O A180603 1,2 %A A180603 _Keenan Pepper_, Sep 11 2010