Regular Elements of the Semigroup B&lt;sub&gt;x&lt;/sub&gt;(D) Defined by Semilattices of the Class Σ&lt;sub&gt;2&lt;/sub&gt;(X,8), when Ζ&lt;sub&gt;7 &lt;/sub&gt;∩ Z&lt;sub&gt;6 &lt;/sub&gt;=Ø and their Calculation Formulas
International journal of pure mathematical sciences