For any natural number N, the number of primes not greater than it is of the order of the logarithm of N. It can be proved also that for any prime p, the next prime is less than 2p. There is no consistency, however; for instance, the nearby numbers 86 629 and 86 677 are both primes, and the virtually adjacent numbers 8 004 119 and 8 004 121 are both primes, called ‘paired primes’. Primes appear to be distributed generally without pattern, but the Mersenne primes provide something of a patterned subset. These develop the fact that 3 = 22 – 1, 7 = 23 – 1, 31 = 25 – 1, and 127 = 27 – 1 to suggest that 2n – 1 is a prime if n is a prime. But the prime n = 11 fails, as do many others. However, the formula holds true for an extended if not unlimited range, for four three-figure primes, for eight four-figure primes, and at least to n = 216 091 (giving a Mersenne prime with over 65 000 decimal digits); it provides one relatively economical means for the esoteric exercise of seeking ever larger prime numbers.
From the Oxford Dictionary of Units and Measures via Answers.com.
I had a friend who once told me “I don’t like to wear shirts with stuff on them because people just ask me about them all the time.” He may or may not feel this way anymore, but I’ve always been of the opposite opinion – wear something you’re proud of! Even with band t-shirts, where there is no easily discernible “cause,” what’s wrong with having a stranger exclaim in delight that he or she has discovered another fan of some obscure European metal band?
With that being said, it can be a bit alienating to wear, say, a Meat is Murder t-shirt, or some of the more abrupt activist messages. But there are more docile and still effective choices. Enter We Add Up, a website devoted to t-shirts that literally count the number of people who bought the shirt and display the resulting number with message on the front.
Every shirt is printed by hand with a unique number. YOUR number is your position in our sequential global count of people who are taking steps to do their part. As the count grows, we demonstrate to the world that “WE ADD UP.”
Genius! And catchy shirts too. They also sell tote bags, biodegradable coffee mugs (made from US corn, though there are detractors to this approach), and the cool “Neither” tote (think: paper or plastic?). In addition they allow groups to sign up to fund-raise with the numerical tees, all while promoting climate solutions and green living. The founding is pretty rad as well: a girl and her mom inspired by the earth’s plight, set off by the simple motto of “do something!”
Here are a couple of my favorites: