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Posets with n points with property that there is no nonsingelton proper subset T for which x not in T implies x<T or x>T or x incomparable with every element of T.
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%I #8 Aug 21 2015 22:45:30

%S 1,1,0,0,24,360,17400,1066800

%N Posets with n points with property that there is no nonsingelton proper subset T for which x not in T implies x<T or x>T or x incomparable with every element of T.

%D J. A. Wright, There are 718 6-point topologies, quasi-orderings and transgraphs, Notices Amer. Math. Soc., 17 (1970), p. 646, Abstract #70T-A106.

%H J. A. Wright, <a href="/A000798/a000798_4.pdf">Letter to N. J. A. Sloane, Apr 06 1972, listing 18 sequences</a>

%H <a href="/index/Pos#posets">Index entries for sequences related to posets</a>

%Y A subset of the posets enumerated in A003431. Cf. A046904.

%K nonn

%O 0,5

%A John A. Wright.