摘要 :
In this paper, we discuss the groups and semigroups of D operators, where D indicates either D（R2） or D （R）. As a special case, we also consider the semigroups of generalized scalar operators and those of scalar operators. One...
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In this paper, we discuss the groups and semigroups of D operators, where D indicates either D（R2） or D （R）. As a special case, we also consider the semigroups of generalized scalar operators and those of scalar operators. One of the main conditions given in A. R. Sourour’s and E. Berkson’s papers has been omitted.
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摘要 :
<正> In [1] an ordered tree is represented by a sequence of non-negative integers, and an algorithm is given to generate lexicographically all ordered trees with n vertices Now on the basis of [1] we define the representative sequence...
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<正> In [1] an ordered tree is represented by a sequence of non-negative integers, and an algorithm is given to generate lexicographically all ordered trees with n vertices Now on the basis of [1] we define the representative sequences of rooted trees and trees, respectively. Then algorithms are given, respectively, to generate lexicographically all rooted trees and trees with n vertices.
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