ملخص
Let Singn be the semigroup of singular self-maps of Xn = {1, ... ,n}, let Rn = {α ∈ Singn: (∀y ∈ Im α)|yα-1| ≥ |Im α|} and let E(Rn) be the set of idempotents of Rn. Then it is shown that Rn = (E(Rn))2. Moreover, expressions for the order of Rn and E(Rn) are obtained in terms of the kth-upper Stirling number of the second kind, S(n,r,k); defined as the number of partitions of Xn into r subsets each of size not less than k.
اللغة الأصلية | English |
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الصفحات (من إلى) | 291-297 |
عدد الصفحات | 7 |
دورية | Discrete Mathematics |
مستوى الصوت | 189 |
رقم الإصدار | 1-3 |
المعرِّفات الرقمية للأشياء | |
حالة النشر | Published - يوليو 28 1998 |
منشور خارجيًا | نعم |
ASJC Scopus subject areas
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