Suppose we write $s(n,k)$ for the Stirling numbers of the first kind. When $p$ is a prime number, I'm interested in knowing when $s(p^a, k)$ is divisible by $p^a$. So:
What is known about $s(p^a,k)$ mod $p^a$ ?
I have tried to ask google about this, but the literature is confusing (there are some congruences that are proved, but it seems difficult to figure out whether this one is among them). I thought that someone here might know the answer from the top of their head.
(Note that I would really like the answer to be "you need to work it out yourself", for it seems like a fun problem. Unfortunately someone else may have done it already.)
Thanks !
Pierre