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 A178435 #17 Aug 01 2023 14:30:24 %S A178435 1,6,162,19602,10619910,25753129470,279488630719746, %T A178435 13573527285845525634,2949851294016821586137934, %U A178435 2868652614504623418332698354038,12483073717920041560887416137620435882,243068197882943244196175524589364487906969746,21178547618859581967063811182618272071362317831449326 %N A178435 Number of acyclic orientations of the n X n X n triangular grid. %C A178435 The n X n X n triangular grid has n rows with i vertices in row i. Each vertex is connected to the neighbors in the same row and up to two vertices in each of the neighboring rows. The graph has A000217(n) vertices and 3*A000217(n-1) edges altogether. %C A178435 An acyclic orientation is an assignment of a direction to each edge such that no cycle in the graph is consistently oriented. Stanley showed that the number of acyclic orientations of a graph G is equal to the absolute value of the chromatic polynomial X_G(q) evaluated at q=-1. %H A178435 Richard P. Stanley, Acyclic Orientations of Graphs, Discrete Mathematics, 5 (1973), pages 171-178, doi:<a href="http://dx.doi.org/10.1016/0012-365X(73)90108-8">10.1016/0012-365X(73)90108-8</a> %H A178435 Wikipedia, <a href="https://en.wikipedia.org/wiki/Chromatic_polynomial">Chromatic polynomial</a> %H A178435 Wikipedia, <a href="https://en.wikipedia.org/wiki/Lattice_graph#Other_kinds">Triangular grid graph</a> %Y A178435 Cf. A182797, A182788, A182789, A182790, A182791, A182792, A182793, A182794, A182795, A182796, A182798, A000217. %K A178435 hard,nonn %O A178435 1,2 %A A178435 _Alois P. Heinz_, Dec 21 2010