Ulam Spiral

The Ulam spiral, or prime spiral (in other languages also called the Ulam Cloth) is a simple method of visualizing the prime numbers that reveals the apparent tendency of certain quadratic polynomials to generate unusually large numbers of primes. It was discovered by the mathematician Stanislaw Ulam in 1963, while he was doodling during the presentation of a "long and very boring paper" at a scientific meeting. Shortly afterwards, in an early application of computer graphics, Ulam with collaborators Myron Stein and Mark Wells used MANIAC II at Los Alamos Scientific Laboratory to produce pictures of the spiral for numbers up to 65,000. In March of the following year, Martin Gardner wrote about the Ulam spiral in his Mathematical Games column; the Ulam spiral featured on the front cover of the issue of Scientific American in which the column appeared.

In an addendum to the Scientific American column, Gardner mentions work of the herpetologist Laurence M. Klauber on two dimensional arrays of prime numbers for finding prime-rich quadratic polynomials which was presented at a meeting of the Mathematical Association of America in 1932–more than thirty years prior to Ulam's discovery. Unlike Ulam's array, Klauber's was not a spiral and had triangular rather than square shape.