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A046907 Number of isomorphism classes of irreducible posets with n labeled points. 1
1, 1, 1, 2, 7, 31, 184, 1351, 12524, 146468, 2177570, 41374407, 1008220289, 31559446774, 1269310589336, 65562045668340, 4345161435996517 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,4

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..16.

G. Brinkmann,  B. D. McKay, Posets on up to 16 Points, Order 19 (2) (2002) 147-179 (Table 1)

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

Index entries for sequences related to posets

FORMULA

G.f.: A(x) = 2-1/B(x), where B(x) is g.f. of A000112. - Vladeta Jovovic, Jan 15 2006

CROSSREFS

Cf. A046908.

Sequence in context: A059037 A245313 A306037 * A091312 A118581 A102159

Adjacent sequences:  A046904 A046905 A046906 * A046908 A046909 A046910

KEYWORD

nonn

AUTHOR

John A. Wright.

EXTENSIONS

More terms from Vladeta Jovovic, Jan 15 2006

STATUS

approved

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Last modified October 16 20:23 EDT 2019. Contains 328103 sequences. (Running on oeis4.)