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 A373894 #10 Jun 23 2024 10:35:27 %S A373894 1,1,1,1,2,3,7,13,36,76,232,562,1860,5025 %N A373894 Number of self-dual lattices on n unlabeled nodes. %C A373894 Lattices whose Hasse diagram looks the same if it is turned upside down. %H A373894 Volker Gebhardt and Stephen Tawn, <a href="https://research-data.westernsydney.edu.au/published/ff5d9c10519311ecb15399911543e199/">Catalogue of unlabelled lattices on up to 16 elements</a>, Western Sydney University (2018). %e A373894 a(5)=3: These are the three lattices. %e A373894 o o o %e A373894 | / \ /|\ %e A373894 o o | o o o %e A373894 | | o \|/ %e A373894 o o | o %e A373894 | \ / %e A373894 o o %e A373894 | %e A373894 o %o A373894 (Sage) sum(L.is_lattice() and L.is_self_dual() for L in Posets(n)) %Y A373894 Cf. A006966 (lattices), A133983 (self-dual posets). %K A373894 nonn,more,hard %O A373894 0,5 %A A373894 _Jukka Kohonen_, Jun 21 2024