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A193674 Number of nonisomorphic systems enumerated by A102896; that is, the number of inequivalent closure operators (or Moore families). 9
1, 2, 5, 19, 184, 14664, 108295846, 2796163199765896 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

REFERENCES

D. E. Knuth, The Art of Computer Programming, Vol. 4, Section 7.1.1

LINKS

Table of n, a(n) for n=0..7.

G. Brinkmann and R. Deklerck, Generation of Union-Closed Sets and Moore Families, arXiv:1701.03751 [math.CO], 2017.

G. Brinkmann and R. Deklerck, Generation of Union-Closed Sets and Moore Families, Journal of Integer Sequences, Vol.21 (2018), Article 18.1.7.

P. Colomb, A. Irlande and O. Raynaud, Counting of Moore Families for n=7, International Conference on Formal Concept Analysis (2010).

CROSSREFS

Equals (1/2)*A193675(n).

Cf. A102894, A102895, A102896, A102897, A108798, A108800.

Sequence in context: A304981 A284860 A108799 * A085871 A202422 A212269

Adjacent sequences:  A193671 A193672 A193673 * A193675 A193676 A193677

KEYWORD

nonn,hard,more

AUTHOR

Don Knuth, Jul 01 2005

EXTENSIONS

a(6) received Aug 17 2005

a(6) corrected by Pierre Colomb, Aug 02 2011

a(7) from Gunnar Brinkmann, Feb 07 2018

STATUS

approved

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Last modified March 25 01:17 EDT 2019. Contains 321450 sequences. (Running on oeis4.)