

A193675


Number of nonisomorphic systems enumerated by A102897; that is, the number of inequivalent Horn functions, under permutation of variables.


8




OFFSET

0,1


COMMENTS

When speaking of inequivalent Boolean functions, three groups of symmetries are typically considered: Complementations only, the Abelian group (2,...,2) of 2^n elements; permutations only, the symmetric group of n! elements; or both complementations and permutations, the octahedral group of 2^n n! elements. In this case only symmetry with respect to the symmetric group is appropriate because complementation affects the property of being a Horn function.


REFERENCES

D. E. Knuth, The Art of Computer Programming, Vol. 4A, Section 7.1.1, p. 79.


LINKS

Table of n, a(n) for n=0..7.
P. Colomb, A. Irlande and O. Raynaud, Counting of Moore Families for n=7, International Conference on Formal Concept Analysis (2010).
D. E. Knuth, HORNCOUNT


CROSSREFS

Equals 2*A193674(n).
Cf. A102894, A102895, A102896, A102897, A108798, A108800.
Sequence in context: A081080 A109460 A108801 * A111022 A086852 A084737
Adjacent sequences: A193672 A193673 A193674 * A193676 A193677 A193678


KEYWORD

nonn,hard,nice,more


AUTHOR

Don Knuth, Jul 01 2005; a(6) received Aug 17 2005


EXTENSIONS

a(6) corrected by Pierre Colomb, Aug 02 2011
a(7) = 2*A193674(7) from Hugo Pfoertner, Jun 18 2018


STATUS

approved



