A. Umar

activity

20102025

most citedCombinatorial results for certain semigroups of order-preserving full contraction mappings of a finite chain

9 citations · 21 across the 20 of their papers we have counts for

collaborators

20 papers

math.GR2025

The monoid of monotone and decreasing partial transformations on a finite chain

Muhammad Mansur Zubairu, Abdullahi Umar, Fatma Salim Al-Kharousi

In this article, we consider the monoid of all monotone and order-decreasing partial transformations denoted as $D O RP_{n}$ on an $n$ ordered chain $[n] = {1, \dots, n}$ ,…

math.GR2025

On the small Schröder semigroup $SS_{n}^{'}$

Muhammad Mansur Zubairu, Abdullahi Umar, Fatma Salim Al-Kharousi

Let $[n]$ be a finite $n -$ chain ${1, 2, \dots, n}$ , and let $LS_{n}$ be the Schröder monoid, consisting of all isotone and order-decreasing partial transformations on $…

math.GR2024

On injective partial Catalan monoids

F. S. Al-Kharousi, A. Umar, M. M. Zubairu

Let $[n]$ be a finite chain ${1, 2, \dots, n}$ , and let $I C_{n}$ be the semigroup consisting of all isotone and order-decreasing injective partial transformations on $…

math.GR2024

On the algebraic structure of the Schröder monoid

Muhammad Mansur Zubairu, Abdullahi Umar, Fatma Salim Al-Kharousi

Let $[n]$ be a finite chain ${1, 2, \dots, n}$ , and let $LS_{n}$ be the semigroup consisting of all isotone and order-decreasing partial transformations on $[n]$ . More…

math.GR2022

On the combinatorial and rank properties of certain subsemigroups of full contractions of a finite chain

Muhammad Mansur Zubairu, Abdullahi Umar, Muhammad Jada Aliyu

Let $[n] = {1, 2, \dots, n}$ be a finite chain and let $C T_{n}$ be the semigroup of full contractions on $[n]$ . Denote $O R C T_{n}$ and $O C T_{n}$ to be th…

math.GR2022★ 1 cited

On certain Semigroup of Order-decreasing Full Contraction Mappings of a Finite Chain

M. M. Zubairu, A. Umar, J. A. Aliyu

Let $C T_{n}$ be the semigroup of full contraction mappings on $[n] = {1, 2, \dots, n}$ , and let $O C T_{n}$ and $O D C T_{n}$ be the subsemigroups consisting of al…

The monoid of monotone and decreasing partial transformations on a finite chain

On the small Schröder semigroup SSn′​

On injective partial Catalan monoids

On the algebraic structure of the Schröder monoid

On the combinatorial and rank properties of certain subsemigroups of full contractions of a finite chain

On certain Semigroup of Order-decreasing Full Contraction Mappings of a Finite Chain

On the small Schröder semigroup $SS_{n}^{'}$