  The material of this work is aimed at mathematics educators, as well as math
specialists with a keen interest in progressions. In this paper, we study the
subject of arithmetic, geometric, mixed, and harmonic progressions or
sequences. Some of the material found in Sections 2,3,4,and 5, can also be
found in standard precalculus texts. For example, refer to the books in
references 1 and 2. A substantial portion of the material in those sections,
cannot be found in such books. In Section 6, we present 21 problems with
detailed solutions. These are interesting, unusual problems not commonly found
in mathematics texts, and most of them are quite challenging. In Section 7, we
offer a collection of unsolved problems.
