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 A192855 #29 Jun 02 2025 04:14:11
%S A192855 1,1,2,5,15,52,203,876,4120,20883,113034,648410,3917021,24785452,
%T A192855 163525976,1120523114,7947399981,58172358642,438300848329,
%U A192855 3391585460591,26898763482122
%N A192855 Number of set partitions of {1, ..., n} that avoid enhanced 4-crossings (or enhanced 4-nestings).
%H A192855 M. Bousquet-Mélou and G. Xin, <a href="https://arxiv.org/abs/math/0506551">On partitions avoiding 3-crossings</a>, arXiv:math/0506551 [math.CO], 2005-2006.
%H A192855 Sophie Burrill, Sergi Elizalde, Marni Mishna and Lily Yen, <a href="https://arxiv.org/abs/1108.5615">A generating tree approach to k-nonnesting partitions and permutations</a>, arXiv preprint arXiv:1108.5615 [math.CO], 2011-2014.
%H A192855 W. Chen, E. Deng, R. Du, R. P. Stanley, and C. Yan, <a href="https://arxiv.org/abs/math/0501230">Crossings and nestings of matchings and partitions</a>, arXiv:math/0501230 [math.CO], 2005.
%H A192855 Juan B. Gil and Jordan O. Tirrell, <a href="https://arxiv.org/abs/1806.09065">A simple bijection for classical and enhanced k-noncrossing partitions</a>, arXiv:1806.09065 [math.CO], 2018-2023. Also Discrete Mathematics (2019) Article 111705, doi:10.1016/j.disc.2019.111705.
%e A192855 There are 877 partitions of 7 elements, but a(7)=51 because the partition {1,7}{2,6}{3,5}{4} has an enhanced 4-nesting.
%Y A192855 Cf. A000110, A108307.
%K A192855 nonn,more
%O A192855 0,3
%A A192855 _Marni Mishna_, Jul 11 2011