I was doing an exercise for my algebra class dealing with the number of abelian groups of order p^n, where p is a prime number, up to isomorphism. i had to fill out a table for n = 2 to n = 8. for example, for n = 2,3,4,5,6,7,8, the number of groups = 2,3,5,7,11,15,22, respectively. essentially, the different ways one can write p^n. for example, for p^5, one can write p^5, p^4 p, p^3 p p, etc... although not part of the question, i was wondering if there was an easy way to work out a formula for this relation given any n? seems interesting, but i haven't come across it yet.