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 A180604 #7 Aug 16 2013 05:16:57 %S A180604 1,6,6,6,12,18,30,30,18,18,36,42,54,54,42,66 %N A180604 Number of "pieces" of the n-th Brillouin zone of a 2D hexagonal lattice. %C A180604 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. %e A180604 The 2nd Brillouin zone consists of 6 equilateral triangles, so a(2) = 6. The 5th Brillouin zone consists of 12 30-60-90 triangles, so a(5) = 12. %K A180604 nonn,more %O A180604 1,2 %A A180604 _Keenan Pepper_, Sep 11 2010