login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A193675 Number of nonisomorphic systems enumerated by A102897; that is, the number of inequivalent Horn functions, under permutation of variables. 8
2, 4, 10, 38, 368, 29328, 216591692, 5592326399531792 (list; graph; refs; listen; history; text; internal format)
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, HORN-COUNT

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

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified September 19 01:08 EDT 2018. Contains 315153 sequences. (Running on oeis4.)