I got a note recently from Don Knuth.
He had exhumed some old notes, on finite algebraic systems with a
binary operator that satisfies the axiom B.AB = A.
He called them Gropes.
I briefly called them Babagroups, as a reminder of the axiom.
The formal name is Semisymmetric Quasigroups.
Don's note includes a short six page summary of Grope properties,
including some constructions and the relationship with Steiner Triples.
It's pretty dense. I haven't fully grokked it, but he doesn't seem
to mention our group's discovery about the number of idempotents mod 3.
The most interesting part was toward the end: He wrote a program
to count the non-isomorphic systems, to contribute to Sloane's
database. He found my numbers (thanks, Neil), hence the note.
Meet me at 1,1,2,3,4,9,41,595,26620,3908953,1867918845.
I'm the guy with purple hair.
Rich
