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 A281574 #31 Aug 30 2022 14:25:26 %S A281574 1,1,0,1,1,1,1,2,1,2,1,3,2,2,3,5,3,4,5,6,6,8,9,16,16,21,29,45,50,95, %T A281574 136,220,392,680,1270,2530,4991 %N A281574 Number of geometric lattices on n nodes. %C A281574 A finite lattice is geometric if it is semimodular and atomistic. Atomistic (or atomic in Stanley's terminology) means that every element is a join of some atoms; or equivalently, that every join-irreducible element is an atom. %C A281574 a(n) is the number of simple matroids with n flats, up to isomorphism. - _Harry Richman_, Jul 27 2022 %H A281574 J. Kohonen, <a href="http://arxiv.org/abs/1708.03750">Generating modular lattices up to 30 elements</a>, arXiv:1708.03750 [math.CO], 2017-2018. %H A281574 M. Malandro, <a href="http://www.shsu.edu/mem037/Lattices.html">The unlabeled lattices on <=15 nodes</a>, (listing of lattices; geometric lattices are a subset of these). %H A281574 Wikipedia, <a href="https://en.wikipedia.org/wiki/Geometric_lattice">Geometric lattice</a> %e A281574 From _Peter Luschny_, Jan 24 2017: (Start) %e A281574 The only two geometric lattices on 8 nodes: %e A281574 7 %e A281574 / | \ %e A281574 / | \ _ _ 7_ _ %e A281574 3 5 6 / / /\ \ \ %e A281574 |\/ \/| / / / \ \ \ %e A281574 |/\ /\| 1 2 3 4 5 6 %e A281574 1 2 4 \ \ \ / / / %e A281574 \ | / \_\_\/_/_/ %e A281574 \|/ 0 %e A281574 0 %e A281574 (End) %Y A281574 Cf. A229202 (semimodular lattices). %K A281574 nonn,more,hard %O A281574 1,8 %A A281574 _Jukka Kohonen_, Jan 24 2017 %E A281574 a(16)-a(34) from Kohonen (2017), by _Jukka Kohonen_, Aug 15 2017 %E A281574 a(35)-a(37) by _Jukka Kohonen_, Jul 07 2020