A076020 Number of systems with n elements with one binary operation satisfying the equation B(AB)=A (semisymmetric quasigroups). This gives numbers of systems which are isomorphic to their transpose but are noncommutative.

0, 0, 0, 1, 3, 6, 24, 178, 1328

Offset

1,5

Links

Table of n, a(n) for n=1..9.

Crossrefs

Cf. A076016-A076021.

Sequence in context: A294381 A081072 A000717 * A018994 A018964 A304186

Adjacent sequences: A076017 A076018 A076019 * A076021 A076022 A076023

Keyword

nonn,hard,more

Author

Richard C. Schroeppel, Oct 29 2002

Status

approved