Originally Posted By: etaoin
some sort of factorial Fibonacci?


I wouldn't make it seem that complicated. It's simply a matter of the factorial of any number. Suppose you have an 8 letter word. For the first position, you have eight choices. Once you've chosen the first letter, you now have 7 letters left over to choose from for the second letter in the word, and so on, so that the number of possible choices for a given position decreases by one each time. Hence 8 x 7 x 6 x 5 x 4 x3 x 2 x 1 = 8! = 40320 combinations of 8 letters. It naturally follows that 9! will be 9 times 8! and so on.