Hi everybody. I am looking for the simplest way to generate "random" numbers given nonrandom input, except I need the output to always be the same, given the same input.

This is a simplification of what I am really doing as part of a website. I want to feature a certain random article as the "Article of the Day." Each day it must change at random. But during the day, one user logging on two different times must see the same one. And two users logging in on the same day must see the same one. I know I can hardcode a list, but I want the algorithm to update itself automatically, and throw new articles in the selection pool as they are added by users (only at the end of each day, though).

I know the function

behaves chaotically when k is between 3 and 4. So an example algorithm might be letting k=3.98 and taking the (N+100)th iteration of the number .5, where N represents the day of the year (1-366). The answer, A, would then be a number between 0 and 1, so A times the number of articles saved in the system would return a whole number that tags a random article.

There are some technical problems with this particular function, and I fear it is overkill. Are there any standard ways of doing what I am describing?