FURRY MATH The Erdős discrepancy problem examines sequences of 1s and –1s or, in this case, puppies and kittens. The goal is to see how effectively one can minimize the difference between the number of cats and dogs in various subsequences. Here, the difference in each row doesn’t exceed one.
Puppy: spxChrome/iStockphoto; Kitten: Tsekhmister/iStockphoto