A. Umar

activity

20102022

most citedA countable family of finitely presented infinite congruence-free monoids

2 citations · 4 across the 10 of their papers we have counts for

collaborators

Showing 2017Show all

2 papers · 1 filter

math.GR2017

Combinatorial results for certain semigroups of order-decreasing partial isometries of a finite chain

F. Al-Kharousi, R. Kehinde, A. Umar

Let $I_{n}$ be the symmetric inverse semigroup on $X_{n} = {1, 2, \dots, n}$ and let $DDP_{n}$ and $O DDP_{n}$ be its subsemigroups of order-decreasing partial isom…

math.GR2017

Presentations for subsemigroups of $P D_{n}$

Abdullahi Umar

Let $[n] = {1, \dots, n}$ be the $n$ -chain. We give presentations for the following transformation semigroups: the semigroup of full order-decreasing mappings of $[n]$ , the semigrou…

Combinatorial results for certain semigroups of order-decreasing partial isometries of a finite chain

Presentations for subsemigroups of PDn​

Presentations for subsemigroups of $P D_{n}$