Let
and
define the set
to be the collection of all bounded analytic functions on the unit disk
in the complex plane
whose
-th derivative
vanishes at zero for all
.
We prove that
is an
algebra precisely when
is an abelian semigroup. In particular, we show that if
is a finite set, then
yielding an algebra
is equivalent to
being a numerical semigroup. Moreover, an algorithm for constructing
when
is
finite is provided. These results answer the questions posed by Ryle (2009). We then
classify some of these sets and give a list of their exact representations.
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