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 A330039 #16 Jun 22 2020 06:56:49
%S A330039 1,1,4,47,3322,11396000
%N A330039 Number of essential lattice congruences of the weak order on the symmetric group S_n.
%H A330039 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 A330039 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 A330039 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 a(3)=4 essential lattice congruences, namely {}, {132=312}, {213=231}, {132=312,213=231}.
%Y A330039 Cf. A091687, A001246, A052528, A024786, A123663, A330040, A330042.
%K A330039 nonn,hard,more
%O A330039 1,3
%A A330039 _Torsten Muetze_, Nov 28 2019