An essential reference for all who love primes by Chris Caldwell and G. L. Honaker, Jr.
It is that joy, that pleasure, that is the heart and soul of the science of numbers: number theory. Yet out of idle ideas often comes real mathematics. For example, Stanislaw Ulam, while sitting bored in a meeting, started writing the numbers in an array, beginning with one and then “spiraling.” When he marked the primes, there seemed to be lines of primes (click on the small image to see a larger one). These lines represent consecutive values of quadratic functions. Ulam’s doodled spiral appeared on the cover of Scientific American the following year (March 1964), and still regularly generates research papers.