| Σ | # | Presentation | Description | Related |
| 8 | 526 | ⟨a, b | aab=a, bbbb=1⟩ | Finite non-commutative monoid with 20 elements | 10 iso, 9 anti-iso |
| 9 | 2207 | ⟨a, b | ab=aa, bbbb=b⟩ | Finite non-commutative monoid with 20 elements | 1 anti-iso |
| 10 | 4095 | ⟨a, b | baa=abb, abab=1⟩ | Finite non-Abelian group with 20 elements | 4 iso, 1 anti-iso |
| 10 | 5349 | ⟨a, b | aaa=bb, bab=aa⟩ | Finite non-commutative monoid with 20 elements | 1 iso |
| 10 | 6728 | ⟨a, b | aba=a, aaaa=bb⟩ | Finite non-commutative monoid with 20 elements | |
| 10 | 6764 | ⟨a, b | aba=b, aaaa=bb⟩ | Finite non-commutative monoid with 20 elements | |
| 10 | 7117 | ⟨a, b | ab=aa, bbbb=bb⟩ | Finite non-commutative monoid with 20 elements | |
| 11 | 12159 | ⟨a, b | aaaa=aa, abbb=b⟩ | Finite non-commutative monoid with 20 elements | |
| 11 | 12322 | ⟨a, b | aaab=bb, bbba=a⟩ | Finite non-commutative monoid with 20 elements | |
| 11 | 14367 | ⟨a, b | aaaa=a, bbbbb=a⟩ | Isomorphic to ℕ(20 = 5) | |
| 11 | 14407 | ⟨a, b | aaaa=b, bbbbb=a⟩ | Isomorphic to ℕ(20 = 1) | |
| 11 | 14408 | ⟨a, b | aaaa=b, bbbbb=b⟩ | Isomorphic to ℕ(20 = 4) | |
| 11 | 15933 | ⟨a, b | aba=bb, baaab=a⟩ | Finite non-commutative monoid with 20 elements | |
| 11 | 16124 | ⟨a, b | aab=aa, baba=bb⟩ | Finite non-commutative monoid with 20 elements | |
| 11 | 16339 | ⟨a, b | aba=aa, aaaa=bb⟩ | Finite non-commutative monoid with 20 elements | |
| 11 | 16343 | ⟨a, b | aba=aa, aaab=bb⟩ | Finite non-commutative monoid with 20 elements | |
| 11 | 16545 | ⟨a, b | aba=bb, abb=aaa⟩ | Finite non-commutative monoid with 20 elements | |
| 11 | 18619 | ⟨a, b | aba=b, aaaaabb=1⟩ | Finite non-Abelian group with 20 elements | 3 iso |
| 11 | 19503 | ⟨a, b | aab=a, bbbbb=bb⟩ | Finite non-commutative monoid with 20 elements | |
| 11 | 21047 | ⟨a, b | ab=aa, bbbb=bbb⟩ | Finite non-commutative monoid with 20 elements | |
| Σ | # | Presentation | Mapping |
| 10 | 4216 | ⟨a, b | aaaaa=1, babbb=1⟩ | φ(a) = bbbbbbbbbbbbbbbb, φ(b) = b |
| 10 | 4217 | ⟨a, b | aaaaa=1, bbabb=1⟩ | φ(a) = bbbbbbbbbbbbbbbb, φ(b) = b |
| 10 | 4381 | ⟨a, b | aaaa=b, bbbbb=1⟩ | φ(a) = b, φ(b) = bbbb |
| 10 | 5447 | ⟨a, b | aaaa=1, abbbbb=1⟩ | φ(a) = bbbbbbbbbbbbbbb, φ(b) = b |
| 10 | 5454 | ⟨a, b | aaaa=1, babbbb=1⟩ | φ(a) = bbbbbbbbbbbbbbb, φ(b) = b |
| 10 | 5456 | ⟨a, b | aaaa=1, bbabbb=1⟩ | φ(a) = bbbbbbbbbbbbbbb, φ(b) = b |
| 10 | 5732 | ⟨a, b | aaaa=1, bbbbb=a⟩ | φ(a) = bbbbb, φ(b) = b |
| 11 | 11691 | ⟨a, b | aaaa=bb, bbbbb=1⟩ | φ(a) = b, φ(b) = bbbbbbbbbbbb |
| 11 | 13287 | ⟨a, b | aaaaa=1, aabbbb=1⟩ | φ(a) = bbbbbbbb, φ(b) = b |
| 11 | 13297 | ⟨a, b | aaaaa=1, abbbba=1⟩ | φ(a) = bbbbbbbb, φ(b) = b |
| 11 | 13302 | ⟨a, b | aaaaa=1, baabbb=1⟩ | φ(a) = bbbbbbbb, φ(b) = b |
| 11 | 13306 | ⟨a, b | aaaaa=1, bbaabb=1⟩ | φ(a) = bbbbbbbb, φ(b) = b |
| 11 | 16606 | ⟨a, b | aaaa=1, abbabbb=1⟩ | φ(a) = bbbbb, φ(b) = bbbbbbbbbbbbbbbbbb |
| 11 | 16608 | ⟨a, b | aaaa=1, abbbabb=1⟩ | φ(a) = bbbbb, φ(b) = bbbbbbbbbbbbbbbbbb |
| 11 | 16623 | ⟨a, b | aaaa=1, babbabb=1⟩ | φ(a) = bbbbb, φ(b) = bbbbbbbbbbbbbbbbbb |
| 11 | 16624 | ⟨a, b | aaaa=1, babbbab=1⟩ | φ(a) = bbbbb, φ(b) = bbbbbbbbbbbbbbbbbb |