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 A330040 #13 Jun 22 2020 06:56:41
%S A330040 1,1,3,19,748,2027309
%N A330040 Number of non-isomorphic cover graphs of lattice quotients of essential lattice congruences of the weak order on the symmetric group S_n.
%H A330040 Hung Phuc Hoang, Torsten Mütze, <a href="https://arxiv.org/abs/1911.12078">Combinatorial generation via permutation languages. II. Lattice congruences</a>, arXiv:1911.12078 [math.CO], 2019.
%H A330040 V. Pilaud and F. Santos, <a href="https://arxiv.org/abs/1711.05353">Quotientopes</a>, arXiv:1711.05353 [math.CO], 2017-2019; Bull. Lond. Math. Soc., 51 (2019), no. 3, 406-420.
%e A330040 For n=3, the weak order on S_3 has the cover relations 123<132, 123<213, 132<312, 213<231, 312<321, 231<321, and there are four essential lattice congruences, namely {}, {132=312}, {213=231}, {132=312,213=231}. The cover graph of the first one is a 6-cycle, the cover graph of the middle two is a 5-cycle, and the cover graph of the last one is a 4-cycle. These are 3 non-isomorphic graphs, showing that a(3)=3.
%Y A330040 Cf. A091687, A001246, A052528, A024786, A123663, A330039, A330042.
%K A330040 nonn,hard
%O A330040 1,3
%A A330040 _Torsten Muetze_, Nov 28 2019