Prime number (prime number): an integer divisible by one and only on its own is so as this definition. Unique guests: numbers 2, 3, 5, 7, 11, 13, 17, 19, 29, 31, 2, 1 ..... because there are only 2 that divides it into, or 17 were 1 to 17 Division it down as well, but it is not the only figure 15 figure 15 = 5x3, so both have 15 1, 3, 5, and 15, which divided it into. Mathematician has to ponder for a long time, and that number only in this universe has a number and the father of Euclid and geometry, Department of mathematics, a great addition the tea kaphu has proven to everyone seemed to 2300 years before that, there are many unique to this universe count, until, overwhelmed by throngs of (infinite)The attention of the mathematician later, is trying to find a formula that will help can tell which number is a unique number? Pierre Fermat math student nationals of France A famous person has proposed a formula to find the number, only that the number is a unique number 22n + 1, no matter what integer is n, for example, when n = 1, we will be number 1 221 1 + 22 + 5 = =, which is the unique number (multiply 2 numbers 22 is itself 2. = 2x2), and n = 2, we will be number 1 1 = 24 + 222 + = 17, which would be unique again, so by replacing the value n = 1, 2, 3, 4, 5, we would be number 17 was 257 and 65537, which is a unique number but enough Swiss mathematician Leonard Euler, rather than n by a 5, he has found that 225 + 1 = 232 + 1 = 4294967297 = 641x6, 700, 417, so no 225 + 1 be unique because both 6700417 and 641 are different, you can divide it down.The formula to find the other formula: n2-n + 41 gives up a number only when n is less than 41 and the formula n2-79n +, 1601, unique as well. When n is less than 80.
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