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A046904 Number of isomorphism classes of 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. 1
1, 1, 0, 0, 1, 4, 28, 234 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,6

REFERENCES

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

LINKS

Table of n, a(n) for n=0..7.

J. A. Wright, Letter to N. J. A. Sloane, Apr 06 1972, listing 18 sequences

Index entries for sequences related to posets

CROSSREFS

A subset of the posets enumerated in A003431. Cf. A046905.

Sequence in context: A229646 A229645 A202824 * A030444 A093877 A151830

Adjacent sequences:  A046901 A046902 A046903 * A046905 A046906 A046907

KEYWORD

nonn

AUTHOR

John A. Wright.

STATUS

approved

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Last modified November 21 11:01 EST 2018. Contains 317447 sequences. (Running on oeis4.)