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”[1] 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.[2][1][3] In March of the following year, Martin Gardner wrote about the Ulam spiral in his Mathematical Games column;[1] the Ulam spiral featured on the front cover of the issue of Scientific American in which the column appeared.

My new motto is "Math every day." I'm giving myself one year to master all the math I was supposed to have learned in high school and college: algebra, geometry, trigonometry, limits and conic sections, differential calculus, integral calculus, multivariate calculus, simple differential equations, linear algebra and eigenvectors/eigenvalues, discrete math and logic, probability and statistics. I "knew" it all at one time or another, without really understanding what the heck it was for, so I should be able to put it all together again fairly quickly, if I put my mind to it.

Math every day. You learn things a little at a time. Practice something every day for half an hour and you'll become comfortable with it in no time.

It gets worse when you ask students to do anything meaningful with fractions. Like: "Explain whether 4/3 or 3/4 is closer to 1, and how you know."

Bonus fact: Want to learn pi to its 20th decimal?  Memorize the following rhyme; the number of letters in each word (ignoring punctuation) is equal to each digit, in order, starting with the 3 before the decimal point:  Pie.  I wish I could calculate pi.  "Eureka!" cried the great inventor: "'Christmas pudding, Christmas pie,' is the problem's very center!"

#5,000: Entirely arbitrary.

Between childhood and adulthood, neural map of the brain rearranges to conceptualize arithmetic