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 A330039 Number of essential lattice congruences of the weak order on the symmetric group S_n. 3
 1, 1, 4, 47, 3322, 11396000 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 LINKS Table of n, a(n) for n=1..6. Hung Phuc Hoang, Torsten Mütze, Combinatorial generation via permutation languages. II. Lattice congruences, arXiv:1911.12078 [math.CO], 2019. V. Pilaud and F. Santos, Quotientopes, arXiv:1711.05353 [math.CO], 2017-2019; Bull. Lond. Math. Soc., 51 (2019), no. 3, 406-420. EXAMPLE 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}. CROSSREFS Cf. A091687, A001246, A052528, A024786, A123663, A330040, A330042. Sequence in context: A210828 A361560 A333247 * A141040 A182102 A052105 Adjacent sequences: A330036 A330037 A330038 * A330040 A330041 A330042 KEYWORD nonn,hard,more AUTHOR Torsten Muetze, Nov 28 2019 STATUS approved

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Last modified December 5 19:51 EST 2023. Contains 367593 sequences. (Running on oeis4.)