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 A284762 #10 Jan 26 2025 20:28:16
%S A284762 1,2,9,69,852,16363,479435,21150888,1388124543,133822887673,
%T A284762 18707633394606,3745998552621317,1062675319801676431,
%U A284762 423005074717335908762,234301896939296139079453,179277553685814268284430793,188286118651948743843774496644,269901723843412313246289232355847,525443899393186663528068248469425039
%N A284762 Total number of subsets of X that are open and closed and connected summed over all distinct topological spaces X that can be placed on an n-set.
%F A284762 E.g.f.: (log(A(exp(x)-1))+1)*A(exp(x)-1) where A(x) is the e.g.f. for A001035.
%e A284762 a(2) = 9. Let X = {a,b}. There are four distinct topologies (A000798) that can be placed on X: {{},X} {{},{a},X} {{}, {b},X} {{},{a},{b},X}. These topologies have 2 + 2 + 2 + 3 sets respectively that are open and closed and connected.
%Y A284762 Cf. A281547.
%K A284762 nonn
%O A284762 0,2
%A A284762 _Geoffrey Critzer_, Apr 02 2017