[6, 15842] finitely based
[6, 15842] is a band: every element is idempotent. It is finitely based: 2 identities define its variety, which 102 other semigroups of order six also generate.
Cayley table
| · | 1 | 2 | 3 | 4 | 5 | 6 |
|---|---|---|---|---|---|---|
| 1 | 1 | 1 | 1 | 1 | 1 | 1 |
| 2 | 1 | 2 | 2 | 4 | 4 | 6 |
| 3 | 1 | 3 | 3 | 5 | 5 | 6 |
| 4 | 1 | 2 | 2 | 4 | 4 | 6 |
| 5 | 1 | 3 | 3 | 5 | 5 | 6 |
| 6 | 6 | 6 | 6 | 6 | 6 | 6 |
The product of the row element and the column element, numbered as in Smallsemi. Blue: idempotents on the diagonal.
Structure
- Smallsemi
- SmallSemigroup(6, 15842)
- Idempotents
- 1, 2, 3, 4, 5, 6
- Zero
- none
- Identity
- none
- Nilpotent
- no
- Commutative
- no
- Regular
- yes
- Group
- no
- 𝒥-classes
- 2
- Rank
- 4, generated by {1, 2, 5, 6}
- Self-dual
- no: the class also stands for the opposite semigroup, with the transposed table
Identity basis
Shortest known basis: 2 identities irredundant
- x ≈ x²
- xyxz ≈ xyz
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: 2 identities
- x ≈ x²
- xyxz ≈ xyz
Lean proof
Endpoint theorem: SemigroupBasis.Generated.Order6FinalL5TransferV3.S6_15842.representative_basis
BasisFor Generated.Order6FinalL5TransferV3.S6_15842.table.semigroup Generated.Order6FinalL5TransferV3.S6_15842.targetBasis
- Table
- The theorem is about the semigroup with exactly this table.
- Method
- transfer from order ≤ 5. A semigroup S with a certified basis lies in the variety of this one, as a subsemigroup; S has order at most five, and this semigroup satisfies the basis of S. Then every identity of this semigroup holds in S and follows from the basis, so the basis of S is a basis here too. This is the final sweep of such transfers.
- Size
- Checking this class alone compiles 49 Lean files with 25,794 lines: the endpoint theorem and everything it imports, the shared library included. All of it is shared with the proofs of other classes.
- Census
- SemiBase.Census.S6_15842 checks that the theorem is about the table of this class and concludes Classified; SemiBase.Catalogue.Order6.S6_15842 is the table, with the elements numbered 0 to 5.
Variety
[6, 15842] generates the variety V[15024]; 102 other semigroups of order six generate it too, and 798 semigroups of order six lie in it. [6, 15842] lies in 33 of the 505 varieties of the census, those whose basis it satisfies.
- Directly above
- Directly below
V[15024] in the inclusion graph, with the varieties above and below it.