I Take a pile of n stones, where n ≥ 1
– Split the pile into two smaller piles of size r and s.
– Repeat until you have n piles of 1 stone each.
I Take the product of all the splits
– So all the r’s and s’s from each split.
I Sum up each of these products.
I Prove that this equals n(n2−1 ) for n ≥ 1 .