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 A271219 #20 Aug 27 2022 04:25:08 %S A271219 1,5,83,28925,7663696588 %N A271219 Number n of antichains of P(En) x En*, ordered by lexicographic order, with En a poset of n elements with no pair of elements ordered, and with En* that same set augmented with an (n+1)th element smaller than all others. %C A271219 This sequence is, more interestingly, the number of logical consequence relations in (n+2)-valued logic, with no order between intermediate values (i.e., values other than 0 and 1), which are truth functional, identical to the standard logical consequence relation on bivalent propositions and value-monotonic (if the relation holds, it is preserved with stronger premises and/or weaker conclusions). See reference below. %C A271219 In n-valued logic with all truth values strictly ordered, the number of logical consequence relations with the same properties is more standard, it corresponds to: A030662. It satisfies the same definition as this sequence except that En should now be understood as a well-ordered set of n elements. %H A271219 E. Chemla, P. Egré and B. Spector, <a href="http://semanticsarchive.net/Archive/GQzYTM4N/Chemla-Egre-Spector-LCrelations.pdf">Characterizing logical consequence in many-valued logics</a>, Ms. CNRS/ENS. J. of Logic and Computation, to appear (2016). %K A271219 nonn,more %O A271219 0,2 %A A271219 _Emmanuel Chemla_, Apr 02 2016