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A046912 Number of irreducible quasiorders with n labeled points. 1
1, 1, 2, 11, 147, 3412, 121553, 6353629, 476850636, 50811255045, 7636459252135, 1610584897516674, 474333338553730879, 194055026319667963777, 109692570582311591696890, 85221064877720762475072503 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

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.

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

FORMULA

E.g.f.: A(x) = 2-1/B(x), where B(x) is e.g.f. of A000798. - Vladeta Jovovic, Jan 10 2006

CROSSREFS

Cf. A046911.

Sequence in context: A268743 A204243 A203203 * A185245 A006122 A111014

Adjacent sequences:  A046909 A046910 A046911 * A046913 A046914 A046915

KEYWORD

nonn,more

AUTHOR

John A. Wright.

EXTENSIONS

Corrected and extended by Vladeta Jovovic, Jan 10 2006

STATUS

approved

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Last modified April 21 20:03 EDT 2019. Contains 322328 sequences. (Running on oeis4.)