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Number of unlabeled topologies with up to n points.
5

%I #5 Aug 03 2019 08:43:41

%S 1,2,5,14,47,186,904,5439,41418,404501,5122188,84623842,1828876351,

%T 51701216248,1908493827243,91755916071736,5729050033597431

%N Number of unlabeled topologies with up to n points.

%e Non-isomorphic representatives of the a(0) = 1 through a(3) = 14 topologies:

%e {} {} {} {}

%e {}{1} {}{1} {}{1}

%e {}{12} {}{12}

%e {}{2}{12} {}{123}

%e {}{1}{2}{12} {}{2}{12}

%e {}{3}{123}

%e {}{23}{123}

%e {}{1}{2}{12}

%e {}{1}{23}{123}

%e {}{3}{23}{123}

%e {}{2}{3}{23}{123}

%e {}{3}{13}{23}{123}

%e {}{2}{3}{13}{23}{123}

%e {}{1}{2}{3}{12}{13}{23}{123}

%Y Partial sums of A001930.

%Y The labeled version is A326878.

%Y Cf. A000612, A000798, A003180, A108800, A193675, A306445, A326867, A326882.

%K nonn

%O 0,2

%A _Gus Wiseman_, Aug 02 2019