[6, 14921] finitely based
[6, 14921] is a semigroup with 3 idempotents. It is finitely based: 2 identities define its variety, which no other semigroup of order six generates.
Cayley table
| · | 1 | 2 | 3 | 4 | 5 | 6 |
|---|---|---|---|---|---|---|
| 1 | 1 | 1 | 1 | 1 | 1 | 1 |
| 2 | 1 | 1 | 1 | 2 | 2 | 2 |
| 3 | 3 | 3 | 3 | 3 | 3 | 3 |
| 4 | 1 | 1 | 3 | 4 | 5 | 6 |
| 5 | 1 | 1 | 3 | 5 | 6 | 4 |
| 6 | 1 | 1 | 3 | 6 | 4 | 5 |
The product of the row element and the column element, numbered as in Smallsemi. Blue: idempotents on the diagonal.
Structure
- Smallsemi
- SmallSemigroup(6, 14921)
- Idempotents
- 1, 3, 4
- Zero
- none
- Identity
- none
- Nilpotent
- no
- Commutative
- no
- Regular
- no
- Group
- no
- 𝒥-classes
- 3
- Rank
- 3, generated by {2, 3, 5}
- Self-dual
- no: the class also stands for the opposite semigroup, with the transposed table
Identity basis
Shortest known basis: 2 identities irredundant
- x²y ≈ xyx
- xy ≈ xy⁴
Irredundant: none of these identities follows from the others; for each, a semigroup satisfies the others but not it. Obtained from a basis certified in Lean by removing identities that follow from the others, with the prover Vampire; the equivalence rests on Vampire's proofs, not on Lean. Shortest known, not known to be minimal.
Basis certified in Lean: 3 identities
- x² ≈ x⁵
- x²y ≈ xyx
- xy ≈ xy⁴
Lean proof
Endpoint theorem: SemigroupBasis.Order6.S6_14921.representative_basis
BasisFor Order6.S6_14921.table.semigroup Order6.S6_14921.basis
- Table
- The theorem is about the semigroup with exactly this table.
- Method
- individual proof. A proof written for this semigroup or a few semigroups, outside the generated and the family proofs.
- Size
- Checking this class alone compiles 40 Lean files with 22,873 lines: the endpoint theorem and everything it imports, the shared library included. Of these, 913 lines are used by the proof of this class and of no other.
- Census
- SemiBase.Census.S6_14921 checks that the theorem is about the table of this class and concludes Classified; SemiBase.Catalogue.Order6.S6_14921 is the table, with the elements numbered 0 to 5.
Variety
[6, 14921] generates the variety V[14921]; no other semigroup of order six generates it, and 2,024 semigroups of order six lie in it. [6, 14921] lies in 2 of the 505 varieties of the census, those whose basis it satisfies.
- Directly above
- Directly below
V[14921] in the inclusion graph, with the varieties above and below it.