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A046908 Number of irreducible posets with n labeled points. 1
1, 1, 1, 7, 97, 2251, 80821, 4305127, 332273257, 36630174931, 5711638291981, 1249898984911567, 381230073532620577, 161042140788424003291, 93667063572594041040421, 74610767840852891620692727 (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..15.

G. Brinkmann,  B. D. McKay, Posets on up to 16 Points, Order 19 (2) (2002) 147-179 (Table III, up to 18 points)

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

Index entries for sequences related to posets

FORMULA

E.g.f.: A(x) = 2-1/B(x), where B(x) is e.g.f. of A001035. - Vladeta Jovovic, Jan 10 2006

CROSSREFS

Cf. A046907.

Sequence in context: A003710 A027837 A174315 * A005014 A201063 A157035

Adjacent sequences:  A046905 A046906 A046907 * A046909 A046910 A046911

KEYWORD

nonn

AUTHOR

John A. Wright.

EXTENSIONS

More terms from Vladeta Jovovic, Jan 10 2006

STATUS

approved

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Last modified December 12 07:31 EST 2019. Contains 329948 sequences. (Running on oeis4.)