It was first noticed by the physicist StanisÃ??aw Ulam in 1963, when he got bored in a meeting and started doodling spirals of numbers. He noticed that, if he makes a spiral of consecutive integers, and circles only the prime numbers, strange diagonal "lines" of prime numbers emerge. This is quite surprising, since we would intuitively expect a random distribution of prime numbers. However, these diagonal segments occur on an impressively large scale, and arbitrarily far from the center of the spiral. The following image is a spiral containing about 4000 primes, and next to it is the same image with some of the diagonal paths highlighted. To explore this phenomenon on a large scale, Ulams Prime Number Spiral generates arbitrarily large spirals, with configurable coloring and other options.