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 A384687 #6 Jun 14 2025 18:43:52 %S A384687 4,42,1292,114976,29735760 %N A384687 Number of elements in the Dedekind-MacNeille completion of the Bruhat order on D_n. %C A384687 This sequence is the number of elements in the Dedekind-MacNeille completion (completion by cuts) of the Bruhat order of the Weyl group D_n. It is a type D analog of A378072. %H A384687 A. Lascoux and M.-P. Schützenberger, <a href="https://doi.org/10.37236/1285">Treillis et bases des groupes de Coxeter</a>, Electron. J. Combin. 3 (1996), #R27. %e A384687 For n=2 the Bruhat order on D_2 consists of four elements, 1 (identity), s1, s2, and s2*s1. Its completion forms the diamond lattice and coincides with the order. %e A384687 s2*s1 %e A384687 / \ %e A384687 s1 s2 %e A384687 \ / %e A384687 1 %Y A384687 Cf. A002866 (group D_n order), A005130 (completion for A_n), A378072 (completion for B_n). %K A384687 nonn,more %O A384687 2,1 %A A384687 _Dmitry I. Ignatov_, Jun 07 2025