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A047684 Number of reduced contexts on n unlabeled objects. 0
1, 2, 9, 126, 13596, 108096891 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Equivalently, number of closure systems on n points, up to isomorphism.

REFERENCES

Bernhard Ganter, Rudolf Wille: Formal Concept Analysis, Springer-Verlag, 1999, ISBN 3-540-62771-5, p. 59.

LINKS

Table of n, a(n) for n=1..6.

CROSSREFS

Sequence in context: A067966 A165327 A090242 * A162955 A197314 A295331

Adjacent sequences:  A047681 A047682 A047683 * A047685 A047686 A047687

KEYWORD

hard,nonn,nice

AUTHOR

Bernhard Ganter (ganter(AT)math.tu-dresden.de)

EXTENSIONS

a(6) from Klaus Hoffmann, Jan 01 2016

STATUS

approved

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Last modified March 26 04:32 EDT 2019. Contains 321481 sequences. (Running on oeis4.)