A047684 Number of reduced contexts on n unlabeled objects.

1, 2, 9, 126, 13596, 108096891

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